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Kang Kooi Wei QS 015/1 Matriculation Programme Examination Semester I Session 2016/2017

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  • Kang Kooi Wei

    QS 015/1

    Matriculation Programme

    Examination

    Semester I

    Session 2016/2017

  • PSPM I QS 015/1 Session

    2016/2017

    Kang Kooi Wei @ KMK Page 2

    1. Solve for ๐‘ and ๐‘ž where ๐‘ โ‰  ๐‘ž, such that (๐‘+๐‘ž๐‘–)

    3๐‘–= (3 + โˆšโˆ’16 โˆ’ ๐‘–3).

    SOLUTION

    (๐‘ + ๐‘ž๐‘–)

    3๐‘–= (3 + โˆšโˆ’16 โˆ’ ๐‘–3)

    ๐‘ + ๐‘ž๐‘– = (3 + โˆšโˆ’16 โˆ’ ๐‘–3)(3๐‘–)

    ๐‘ + ๐‘ž๐‘– = (3 + โˆš16โˆšโˆ’1 โˆ’ ๐‘–3)(3๐‘–)

    ๐‘ + ๐‘ž๐‘– = (3 + 4๐‘– โˆ’ ๐‘–3)(3๐‘–)

    ๐‘ + ๐‘ž๐‘– = 9๐‘– + 12๐‘–2 โˆ’ 3๐‘–4

    ๐‘ + ๐‘ž๐‘– = 9๐‘– + 12(โˆ’1) โˆ’ 3(1)

    ๐‘ + ๐‘ž๐‘– = 9๐‘– โˆ’ 15

    ๐‘ + ๐‘ž๐‘– = โˆ’15 + 9๐‘–

    ๐’‘ = โˆ’๐Ÿ๐Ÿ“, ๐’’ = ๐Ÿ—

  • PSPM I QS 015/1 Session

    2016/2017

    Kang Kooi Wei @ KMK Page 3

    2. Determine the values of x which satisfy the equation 32๐‘ฅโˆ’1 = 4(3๐‘ฅ) โˆ’ 9.

    SOLUTION

    32๐‘ฅโˆ’1 = 4(3๐‘ฅ) โˆ’ 9

    32๐‘ฅ3โˆ’1 = 4(3๐‘ฅ) โˆ’ 9

    (3๐‘ฅ)2 (1

    3) = 4(3๐‘ฅ) โˆ’ 9

    (1

    3) (3๐‘ฅ)2 = 4(3๐‘ฅ) โˆ’ 9

    (3๐‘ฅ)2 = 12(3๐‘ฅ) โˆ’ 27

    ๐ฟ๐‘’๐‘ก ๐‘ฆ = 3๐‘ฅ

    (๐‘ฆ)2 = 12(๐‘ฆ) โˆ’ 27

    ๐‘ฆ2 โˆ’ 12๐‘ฆ + 27 = 0

    (๐‘ฆ โˆ’ 3)(๐‘ฆ โˆ’ 9) = 0

    ๐‘ฆ = 3 ๐‘ฆ = 9

    3๐‘ฅ = 3 3๐‘ฅ = 9

    ๐‘ฅ = 1 ๐‘ฅ = 2

  • PSPM I QS 015/1 Session

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    Kang Kooi Wei @ KMK Page 4

    3. The seventh term of a geometric series is 16, the fifth term is 8 and the sum of

    the first ten terms is positive. Find the first term and the common ratio. Hence,

    show that ๐‘†12 = 126(โˆš2 + 1).

    SOLUTION

    Geometric series

    ๐‘ฎ๐’†๐’๐’Ž๐’†๐’•๐’“๐’Š๐’„ ๐’”๐’†๐’“๐’Š๐’†๐’” ๐‘ป๐’ = ๐’‚๐’“๐’โˆ’๐Ÿ

    ๐‘‡7 = ๐‘Ž๐‘Ÿ6 = 16 โ€ฆโ€ฆ (1)

    ๐‘‡5 = ๐‘Ž๐‘Ÿ4 = 8 โ€ฆโ€ฆ (2)

    (1) รท (2)

    ๐‘Ž๐‘Ÿ6

    ๐‘Ž๐‘Ÿ4=

    16

    8

    ๐‘Ÿ2 = 2

    ๐‘Ÿ = ยฑโˆš2

    ๐‘Šโ„Ž๐‘’๐‘› ๐‘Ÿ = ยฑโˆš2

    ๐‘Ž(ยฑโˆš2)4

    = 8

    4๐‘Ž = 8

    ๐‘Ž = 2

  • PSPM I QS 015/1 Session

    2016/2017

    Kang Kooi Wei @ KMK Page 5

    ๐‘ฎ๐’†๐’๐’Ž๐’†๐’•๐’“๐’Š๐’„ ๐’”๐’†๐’“๐’Š๐’†๐’” ๐‘บ๐’ =๐’‚(๐’“๐’ โˆ’ ๐Ÿ)

    ๐’“ โˆ’ ๐Ÿ

    Given that ๐‘บ๐’ > ๐ŸŽ

    Given that ๐‘บ๐’ > ๐ŸŽ

    ๐‘บ๐Ÿ๐ŸŽ =๐’‚(๐’“๐Ÿ๐ŸŽ โˆ’ ๐Ÿ)

    ๐’“ โˆ’ ๐Ÿ

    ๐‘Šโ„Ž๐‘’๐‘› ๐‘Ž = 2; ๐‘Ÿ = โˆš2

    ๐‘†10 =2 [(โˆš2)

    10โˆ’ 1]

    โˆš2 โˆ’ 1

    =2[32 โˆ’ 1]

    โˆš2 โˆ’ 1

    =62

    โˆš2 โˆ’ 1

    = 149.68

    ๐‘Šโ„Ž๐‘’๐‘› ๐‘Ž = 2; ๐‘Ÿ = โˆ’โˆš2

    ๐‘†10 =2 [(โˆ’โˆš2)

    10โˆ’ 1]

    โˆ’โˆš2 โˆ’ 1

    =2[32 โˆ’ 1]

    โˆ’โˆš2 โˆ’ 1

    =62

    โˆ’โˆš2 โˆ’ 1

    = โˆ’25.68

    ๐บ๐‘–๐‘ฃ๐‘’๐‘› ๐‘กโ„Ž๐‘Ž๐‘ก ๐‘†๐‘› > 0, ๐‘Ž = 2 ๐‘Ÿ = โˆš2

  • PSPM I QS 015/1 Session

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    Kang Kooi Wei @ KMK Page 6

    ๐‘†12 =2 [(โˆš2)

    12โˆ’ 1]

    โˆš2 โˆ’ 1

    =2[64 โˆ’ 1]

    โˆš2 โˆ’ 1

    =126

    โˆš2 โˆ’ 1

    =126

    โˆš2 โˆ’ 1 ๐‘ฅ

    โˆš2 + 1

    โˆš2 + 1

    =126(โˆš2 + 1)

    2 + โˆš2 โˆ’ โˆš2 โˆ’ 1

    =126(โˆš2 + 1)

    1

    = 126(โˆš2 + 1)

  • PSPM I QS 015/1 Session

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    Kang Kooi Wei @ KMK Page 7

    4. If A and B are 2 ๐‘ฅ 2 matrices where ๐ต โ‰  ๐ผ2, such that (๐ด + ๐ต)2 = ๐ด2 + 2๐ด๐ต + ๐ต2,

    deduce that ๐ต = ๐ดโˆ’1 [Assume ๐ด๐ต = ๐ต๐ด = ๐ผ]. If ๐ด = [1 29 โˆ’1

    ], find ๐ต.

    SOLUTION

    (๐ด + ๐ต)2 = ๐ด2 + 2๐ด๐ต + ๐ต2

    (๐ด + ๐ต)(๐ด + ๐ต) = ๐ด2 + 2๐ด๐ต + ๐ต2

    ๐ด2 + ๐ด๐ต + ๐ต๐ด + ๐ต2 = ๐ด2 + 2๐ด๐ต + ๐ต2

    ๐ด๐ต + ๐ต๐ด = 2๐ด๐ต

    ๐ต๐ด = 2๐ด๐ต โˆ’ ๐ด๐ต

    ๐ต๐ด = ๐ด๐ต

    โˆด ๐ต = ๐ดโˆ’1

    ๐ด = [1 29 โˆ’1

    ]

    ๐ต = ๐ดโˆ’1 =1

    (1)(โˆ’1) โˆ’ (2)(9)[โˆ’1 โˆ’2โˆ’9 1

    ]

    =1

    โˆ’19[โˆ’1 โˆ’2โˆ’9 1

    ]

    =1

    โˆ’19[โˆ’1 โˆ’2โˆ’9 1

    ]

    = [

    1

    19

    2

    199

    19

    1

    19

    ]

    ๐ผ๐‘“ ๐ด๐ต = ๐ต๐ด = ๐ผ ๐‘กโ„Ž๐‘’๐‘› ๐ตโˆ’1 = ๐ด

  • PSPM I QS 015/1 Session

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    Kang Kooi Wei @ KMK Page 8

    5. (a) Obtain the expansion for (1 โˆ’๐‘ฅ

    4)

    1

    4 in ascending powers of x up to the term ๐‘ฅ3.

    State the interval for x such that the expansion (1 โˆ’๐‘ฅ

    4)

    1

    4 is valid. Hence, obtain

    the simplest form of the expansion (16 โˆ’ 4๐‘ฅ)1

    4.

    (b) Write โˆš124

    in the form of ๐พ [(1 โˆ’๐‘ฅ

    4)

    1

    4]. Hence, approximate โˆš12

    4 correct to

    three decimal places.

    SOLUTION

    a) (1 โˆ’๐‘ฅ

    4)

    1

    4= 1 +

    (1

    4)

    1!(โˆ’

    ๐‘ฅ

    4)1+

    (1

    4)(

    1

    4โˆ’1)

    2!(โˆ’

    ๐‘ฅ

    4)2+

    (1

    4)(

    1

    4โˆ’1)(

    1

    4โˆ’2)

    3!(โˆ’

    ๐‘ฅ

    4)3+ โ‹ฏ

    = 1 + (1

    4) (โˆ’

    ๐‘ฅ

    4) +

    (14) (โˆ’

    34)

    2๐‘ฅ1(๐‘ฅ2

    16) +

    (14) (โˆ’

    34) (โˆ’

    74)

    3๐‘ฅ2๐‘ฅ1(โˆ’

    ๐‘ฅ3

    64) + โ‹ฏ

    = 1 โˆ’๐‘ฅ

    16โˆ’

    3

    32(๐‘ฅ2

    16) โˆ’

    21

    384(๐‘ฅ3

    64) + โ‹ฏ

    = 1 โˆ’1

    16๐‘ฅ โˆ’

    3

    512๐‘ฅ2 โˆ’

    7

    8192๐‘ฅ3 + โ‹ฏ

    The interval for x such that the expansion (๐Ÿ โˆ’๐’™

    ๐Ÿ’)

    ๐Ÿ

    ๐Ÿ’ is valid

    |๐‘ฅ

    4| < 1

    โˆ’1 <๐‘ฅ

    4< 1

    โˆ’4 < ๐‘ฅ < 4

  • PSPM I QS 015/1 Session

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    Kang Kooi Wei @ KMK Page 9

    The simplest form of the expansion (๐Ÿ๐Ÿ” โˆ’ ๐Ÿ’๐’™)๐Ÿ

    ๐Ÿ’

    (16 โˆ’ 4๐‘ฅ)14 = [16(1 โˆ’

    4๐‘ฅ

    16)]

    14

    = 1614 (1 โˆ’

    ๐‘ฅ

    4)

    14

    = 2(1 โˆ’๐‘ฅ

    4)

    14

    = 2 [1 โˆ’1

    16๐‘ฅ โˆ’

    3

    512๐‘ฅ2 โˆ’

    7

    8192๐‘ฅ3 + โ‹ฏ]

    = 2 โˆ’1

    8๐‘ฅ โˆ’

    3

    256๐‘ฅ2 โˆ’

    7

    4096๐‘ฅ3 + โ‹ฏ

    b) โˆš๐Ÿ๐Ÿ๐Ÿ’

    in the form of ๐‘ฒ[(๐Ÿ โˆ’๐’™

    ๐Ÿ’)

    ๐Ÿ

    ๐Ÿ’]

    โˆš124

    = 1214

    = (16 โˆ’ 4)14

    = [16 (1 โˆ’4

    16)]

    14

    = 1614 (1 โˆ’

    1

    4)

    14

    = 2(1 โˆ’1

    4)

    14

    = 2 โˆ’1

    8(1) โˆ’

    3

    256(1)2 โˆ’

    7

    4096(1)3 + โ‹ฏ

    โ‰ˆ 1.862

    2 (1 โˆ’๐‘ฅ

    4)

    14

    = 2 โˆ’1

    8๐‘ฅ โˆ’

    3

    256๐‘ฅ2 โˆ’

    7

    4096๐‘ฅ3

    + โ‹ฏ

    Compare

  • PSPM I QS 015/1 Session

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    Kang Kooi Wei @ KMK Page 10

    6. Given ๐‘“(๐‘ฅ) = ๐‘ฅ2+1

    5, ๐‘ฅ โ‰ฅ 0.

    (a) Determine ๐‘“โˆ’1(๐‘ฅ). Hence, if ๐‘“(๐‘”(๐‘ฅ)) =1

    5(๐‘’2(3๐‘ฅโˆ’1) + 1), show that ๐‘”(๐‘ฅ) =

    ๐‘’3๐‘ฅโˆ’1

    (b) Evaluate ๐‘”(๐‘“(2)) correct to three decimal places.

    (c) Assume that the domain for ๐‘”(๐‘ฅ) is ๐‘ฅ โ‰ฅ 0, determine ๐‘”โˆ’1(๐‘ฅ) and state its

    domain and range.

    SOLUTION

    a) ๐‘“(๐‘ฅ) = ๐‘ฅ2+1

    5, ๐‘ฅ โ‰ฅ 0

    Method I Method II

    ๐‘“(๐‘ฅ) = ๐‘ฅ2 + 1

    5

    ๐‘“[๐‘“โˆ’1(๐‘ฅ)] = ๐‘ฅ

    [๐‘“โˆ’1(๐‘ฅ)]2 + 1

    5= ๐‘ฅ

    [๐‘“โˆ’1(๐‘ฅ)]2 + 1 = 5๐‘ฅ

    [๐‘“โˆ’1(๐‘ฅ)]2 = 5๐‘ฅ โˆ’ 1

    ๐‘“โˆ’1(๐‘ฅ) = โˆš5๐‘ฅ โˆ’ 1

    ๐‘ฆ = ๐‘ฅ2 + 1

    5

    5๐‘ฆ = ๐‘ฅ2 + 1

    ๐‘ฅ2 = 5๐‘ฆ โˆ’ 1

    ๐‘ฅ = โˆš5๐‘ฆ โˆ’ 1

    ๐‘“โˆ’1(๐‘ฅ) = โˆš5๐‘ฅ โˆ’ 1

    ๐‘“(๐‘”(๐‘ฅ)) =1

    5(๐‘’2(3๐‘ฅโˆ’1) + 1)

    [๐‘”(๐‘ฅ)]2 + 1

    5=

    1

    5(๐‘’2(3๐‘ฅโˆ’1) + 1)

    [๐‘”(๐‘ฅ)]2 + 1 = ๐‘’2(3๐‘ฅโˆ’1) + 1

    [๐‘”(๐‘ฅ)]2 = ๐‘’2(3๐‘ฅโˆ’1)

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    ๐‘”(๐‘ฅ) = [๐‘’2(3๐‘ฅโˆ’1)]12

    ๐‘”(๐‘ฅ) = ๐‘’3๐‘ฅโˆ’1

    b) Evaluate ๐‘”(๐‘“(2))

    ๐‘“(2) =22 + 1

    5

    = 1

    ๐‘”(๐‘“(2)) = ๐‘”(1)

    = ๐‘’3(1)โˆ’1

    = ๐‘’2

    c) ๐‘”(๐‘ฅ) = ๐‘’3๐‘ฅโˆ’1

    Method I Method II

    ๐‘”(๐‘ฅ) = ๐‘’3๐‘ฅโˆ’1

    ๐‘”[๐‘”โˆ’1(๐‘ฅ)] = ๐‘ฅ

    ๐‘’3[๐‘”โˆ’1(๐‘ฅ)]โˆ’1 = ๐‘ฅ

    ln ๐‘’3[๐‘”โˆ’1(๐‘ฅ)]โˆ’1 = ln๐‘ฅ

    3[๐‘”โˆ’1(๐‘ฅ)] โˆ’ 1 = ln ๐‘ฅ

    3[๐‘”โˆ’1(๐‘ฅ)] = ln ๐‘ฅ + 1

    ๐‘”โˆ’1(๐‘ฅ) =ln ๐‘ฅ + 1

    3

    ๐‘”(๐‘ฅ) = ๐‘’3๐‘ฅโˆ’1

    ๐‘ฆ = ๐‘’3๐‘ฅโˆ’1

    ln ๐‘ฆ = ln ๐‘’3๐‘ฅโˆ’1

    ln ๐‘ฆ = 3๐‘ฅ โˆ’ 1

    3๐‘ฅ = ln๐‘ฆ + 1

    ๐‘ฅ =ln๐‘ฆ + 1

    3

    ๐‘”โˆ’1(๐‘ฅ) =ln ๐‘ฅ + 1

    3

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    ๐‘”(๐‘ฅ) = ๐‘’3๐‘ฅโˆ’1; ๐‘ฅ โ‰ฅ 0

    ๐ท๐‘”(๐‘ฅ): ๐‘ฅ โ‰ฅ 0 ๐‘…๐‘”(๐‘ฅ): ๐‘ฆ โ‰ฅ ๐‘’3(0)โˆ’1

    ๐‘ฆ โ‰ฅ ๐‘’โˆ’1

    ๐‘ฆ โ‰ฅ1

    ๐‘’

    ๐ท๐‘”โˆ’1(๐‘ฅ) = ๐‘…๐‘”(๐‘ฅ) ๐‘…๐‘”โˆ’1(๐‘ฅ) = ๐ท๐‘”(๐‘ฅ)

    ๐ท๐‘”โˆ’1(๐‘ฅ): ๐‘ฅ โ‰ฅ1

    ๐‘’ ๐‘…๐‘”โˆ’1(๐‘ฅ): ๐‘ฆ โ‰ฅ 0

  • PSPM I QS 015/1 Session

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    7. (a) If โˆš7 โˆ’ 3โˆš5 = โˆš๐‘ฅ โˆ’ โˆš๐‘ฆ, determine the values of ๐‘ฅ and ๐‘ฆ.

    (b) Solve the equation ๐‘™๐‘œ๐‘”2 ๐‘ฅ โˆ’ ๐‘™๐‘œ๐‘”4(3๐‘ฅ + 4) = 0.

    SOLUTION

    a) โˆš7 โˆ’ 3โˆš5 = โˆš๐‘ฅ โˆ’ โˆš๐‘ฆ

    [โˆš7 โˆ’ 3โˆš5]

    2

    = [โˆš๐‘ฅ โˆ’ โˆš๐‘ฆ]2

    7 โˆ’ 3โˆš5 = โˆš๐‘ฅ2+ โˆš๐‘ฆ

    2โˆ’ 2โˆš๐‘ฅโˆš๐‘ฆ

    7 โˆ’ 3โˆš5 = ๐‘ฅ + ๐‘ฆ โˆ’ 2โˆš๐‘ฅ๐‘ฆ

    ๐‘ฅ + ๐‘ฆ = 7

    ๐‘ฆ = 7 โˆ’ ๐‘ฅ โ€ฆโ€ฆโ€ฆโ€ฆโ€ฆโ€ฆโ€ฆ (1)

    2โˆš๐‘ฅ๐‘ฆ = 3โˆš5

    โˆš4๐‘ฅ๐‘ฆ = โˆš9๐‘ฅ5

    4๐‘ฅ๐‘ฆ = 45 โ€ฆโ€ฆโ€ฆโ€ฆโ€ฆโ€ฆโ€ฆ (2)

    Substitute (1) into (2)

    4๐‘ฅ(7 โˆ’ ๐‘ฅ) = 45

    28๐‘ฅ โˆ’ 4๐‘ฅ2 = 45

    4๐‘ฅ2 โˆ’ 28๐‘ฅ + 45 = 0

    (2๐‘ฅ โˆ’ 9)(2๐‘ฅ โˆ’ 5) = 0

    ๐‘ฅ =9

    2 ๐‘ฅ =

    5

    2

  • PSPM I QS 015/1 Session

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    ๐‘ฆ = 7 โˆ’9

    2 ๐‘ฆ = 7 โˆ’

    5

    2

    ๐‘ฆ =5

    2 ๐‘ฆ =

    9

    2

    โˆด ๐‘ฅ =9

    2, ๐‘ฆ =

    5

    2 ๐‘œ๐‘Ÿ ๐‘ฅ =

    5

    2, ๐‘ฆ =

    9

    2

    b) ๐‘™๐‘œ๐‘”2 ๐‘ฅ โˆ’ ๐‘™๐‘œ๐‘”4(3๐‘ฅ + 4) = 0

    ๐‘™๐‘œ๐‘”2 ๐‘ฅ โˆ’๐‘™๐‘œ๐‘”2(3๐‘ฅ + 4)

    ๐‘™๐‘œ๐‘”24= 0

    ๐‘™๐‘œ๐‘”2 ๐‘ฅ โˆ’๐‘™๐‘œ๐‘”2(3๐‘ฅ + 4)

    ๐‘™๐‘œ๐‘”222

    = 0

    ๐‘™๐‘œ๐‘”2 ๐‘ฅ โˆ’๐‘™๐‘œ๐‘”2(3๐‘ฅ + 4)

    2๐‘™๐‘œ๐‘”22= 0

    ๐‘™๐‘œ๐‘”2 ๐‘ฅ โˆ’๐‘™๐‘œ๐‘”2(3๐‘ฅ + 4)

    2(1)= 0

    ๐‘™๐‘œ๐‘”2 ๐‘ฅ โˆ’1

    2๐‘™๐‘œ๐‘”2(3๐‘ฅ + 4) = 0

    ๐‘™๐‘œ๐‘”2 ๐‘ฅ =1

    2๐‘™๐‘œ๐‘”2(3๐‘ฅ + 4)

    ๐‘™๐‘œ๐‘”2 ๐‘ฅ = ๐‘™๐‘œ๐‘”2(3๐‘ฅ + 4)12

    ๐‘ฅ = (3๐‘ฅ + 4)12

    ๐‘ฅ2 = 3๐‘ฅ + 4

    ๐‘ฅ2 โˆ’ 3๐‘ฅ โˆ’ 4 = 0

    (๐‘ฅ โˆ’ 4)(๐‘ฅ + 1) = 0

    ๐‘ฅ = 4 ๐‘œ๐‘Ÿ ๐‘ฅ = โˆ’1

    ๐‘†๐‘–๐‘›๐‘๐‘’ ๐‘ฅ > 0, โˆด ๐‘ฅ = 4

    ๐‘™๐‘œ๐‘”๐‘Ž๐‘ =๐‘™๐‘œ๐‘”๐‘๐‘

    ๐‘™๐‘œ๐‘”๐‘๐‘Ž

    log ๐‘๐‘› = ๐‘› ๐‘™๐‘œ๐‘” ๐‘

    ๐‘™๐‘œ๐‘”๐‘Ž๐‘Ž = 1

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    8. (a) Solve the following equation |3

    ๐‘ฅโˆ’4| = 7, ๐‘ฅ โ‰  4.

    (b) Find the solution set for the inequality, โˆ’4โˆ’๐‘ฅ

    ๐‘ฅโˆ’3โ‰ฅ ๐‘ฅ + 4, ๐‘ฅ โ‰  3.

    SOLUTION

    (a) |3

    ๐‘ฅโˆ’4| = 7

    3

    ๐‘ฅโˆ’4= 7 or

    3

    ๐‘ฅโˆ’4= โˆ’7

    3 = 7(๐‘ฅ โˆ’ 4) 3 = โˆ’7(๐‘ฅ โˆ’ 4)

    3 = 7๐‘ฅ โˆ’ 28 3 = โˆ’7๐‘ฅ + 28

    7๐‘ฅ = 3 + 28 7๐‘ฅ = 28 โˆ’ 3

    7๐‘ฅ = 31 7๐‘ฅ = 25

    ๐‘ฅ =31

    7 ๐‘ฅ =

    25

    7

    (b) โˆ’4โˆ’๐‘ฅ

    ๐‘ฅโˆ’3โ‰ฅ ๐‘ฅ + 4, ๐‘ฅ โ‰  3

    โˆ’4 โˆ’ ๐‘ฅ

    ๐‘ฅ โˆ’ 3โ‰ฅ ๐‘ฅ + 4

    โˆ’4 โˆ’ ๐‘ฅ

    ๐‘ฅ โˆ’ 3โˆ’ ๐‘ฅ โˆ’ 4 โ‰ฅ 0

    โˆ’4 โˆ’ ๐‘ฅ โˆ’ ๐‘ฅ(๐‘ฅ โˆ’ 3) โˆ’ 4(๐‘ฅ โˆ’ 3)

    ๐‘ฅ โˆ’ 3โ‰ฅ 0

    โˆ’4 โˆ’ ๐‘ฅ โˆ’ ๐‘ฅ2 + 3๐‘ฅ โˆ’ 4๐‘ฅ + 12

    ๐‘ฅ โˆ’ 3โ‰ฅ 0

    โˆ’๐‘ฅ2 โˆ’ 2๐‘ฅ + 8

    ๐‘ฅ โˆ’ 3โ‰ฅ 0

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    โˆ’(๐‘ฅ2 + 2๐‘ฅ โˆ’ 8)

    ๐‘ฅ โˆ’ 3โ‰ฅ 0

    (๐‘ฅ2 + 2๐‘ฅ โˆ’ 8)

    ๐‘ฅ โˆ’ 3โ‰ค 0

    (๐‘ฅ + 4)(๐‘ฅ โˆ’ 2)

    ๐‘ฅ โˆ’ 3โ‰ค 0

    (๐‘ฅ + 4) = 0 (๐‘ฅ โˆ’ 2) = 0 (๐‘ฅ โˆ’ 3) = 0

    ๐‘ฅ = โˆ’4 ๐‘ฅ = 2 ๐‘ฅ = 3

    (โˆ’โˆž,โˆ’๐Ÿ’) (โˆ’๐Ÿ’, ๐Ÿ) (๐Ÿ, ๐Ÿ‘) (๐Ÿ‘,โˆž)

    (๐‘ฅ + 4) - + + +

    (๐‘ฅ โˆ’ 2) - - + +

    (๐‘ฅ โˆ’ 3) - - - +

    (๐’™ + ๐Ÿ’)(๐’™ โˆ’ ๐Ÿ)

    ๐’™ โˆ’ ๐Ÿ‘ - + - +

    โˆด ๐‘†๐‘œ๐‘™๐‘ข๐‘ก๐‘–๐‘œ๐‘› ๐‘ ๐‘’๐‘ก; {๐‘ฅ: โˆ’ โˆž < ๐‘ฅ โ‰ค โˆ’4 โˆช 2 โ‰ค ๐‘ฅ < 3}

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  • PSPM I QS 015/1 Session

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    9. Given ๐‘“(๐‘ฅ) = ๐‘’๐‘ฅ and ๐‘”(๐‘ฅ) = |๐‘ฅ โˆ’ 3|.

    (a) Show that (๐‘“ ๐‘”)(๐‘ฅ) = {๐‘’๐‘ฅโˆ’3, ๐‘ฅ โ‰ฅ 3

    ๐‘’โˆ’(๐‘ฅโˆ’3), ๐‘ฅ < 3

    (b) Sketch the graph of ๐‘ฆ = (๐‘“ ๐‘”)(๐‘ฅ). Hence, state the interval in which

    (๐‘“ ๐‘”)โˆ’1(๐‘ฅ) exists.

    (c) Determine (๐‘“ ๐‘”)โˆ’1(๐‘ฅ),for ๐‘ฅ โ‰ฅ 3.

    (d) Find the function โ„Ž(๐‘ฅ) for ๐‘ฅ >1

    3, given that (โ„Ž ๐‘“)(๐‘ฅ) =

    2๐‘’๐‘ฅ

    1โˆ’3๐‘’๐‘ฅ. Hence, show

    that h(x) is a one to one function.

    SOLUTION

    ๐‘“(๐‘ฅ) = ๐‘’๐‘ฅ and ๐‘”(๐‘ฅ) = |๐‘ฅ โˆ’ 3|

    a) (๐‘“ ๐‘”)(๐‘ฅ) = ๐‘“(|๐‘ฅ โˆ’ 3|)

    = ๐‘’|๐‘ฅโˆ’3|

    |๐‘ฅ โˆ’ 3| = {๐‘ฅ โˆ’ 3, ๐‘ฅ โˆ’ 3 โ‰ฅ 0

    โˆ’(๐‘ฅ โˆ’ 3), ๐‘ฅ โˆ’ 3 < 0

    = {๐‘ฅ โˆ’ 3, ๐‘ฅ โ‰ฅ 3

    โˆ’(๐‘ฅ โˆ’ 3), ๐‘ฅ < 3

    (๐‘“ ๐‘”)(๐‘ฅ) = ๐‘’|๐‘ฅโˆ’3|

    = {๐‘’๐‘ฅโˆ’3, ๐‘ฅ โ‰ฅ 3

    ๐‘’โˆ’(๐‘ฅโˆ’3), ๐‘ฅ < 3

    b)

    |๐‘ฅ| = {๐‘ฅ, ๐‘ฅ โ‰ฅ 0

    โˆ’๐‘ฅ, ๐‘ฅ < 0

    ๐‘ฅ

    ๐‘ฆ

    ๐‘’3

    1

    3

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    (๐‘“ ๐‘”)โˆ’1(๐‘ฅ) exists for ๐‘ฅ โ‰ฅ 3 ๐‘œ๐‘Ÿ ๐‘ฅ < 3

    c) (๐‘“ ๐‘”)โˆ’1(๐‘ฅ) ๐‘“๐‘œ๐‘Ÿ ๐‘ฅ โ‰ฅ 3

    (๐‘“ ๐‘”)(๐‘ฅ) = ๐‘’๐‘ฅโˆ’3

    ๐‘ฆ = ๐‘’๐‘ฅโˆ’3

    ln ๐‘ฆ = ln ๐‘’๐‘ฅโˆ’3

    ln ๐‘ฆ = ๐‘ฅ โˆ’ 3

    ๐‘ฅ = ln๐‘ฆ + 3

    โˆด (๐‘“ ๐‘”)โˆ’1(๐‘ฅ) = ln ๐‘ฅ + 3

    d) ๐‘“(๐‘ฅ) = ๐‘’๐‘ฅ,

    (โ„Ž ๐‘“)(๐‘ฅ) =2๐‘’๐‘ฅ

    1 โˆ’ 3๐‘’๐‘ฅ

    โ„Ž[๐‘“(๐‘ฅ)] =2๐‘’๐‘ฅ

    1 โˆ’ 3๐‘’๐‘ฅ

    โ„Ž[๐‘’๐‘ฅ] =2๐‘’๐‘ฅ

    1 โˆ’ 3๐‘’๐‘ฅ

    ๐ฟ๐‘’๐‘ก ๐‘ฆ = ๐‘’๐‘ฅ

    โ„Ž[๐‘ฆ] =2๐‘ฆ

    1 โˆ’ 3๐‘ฆ

    โ„Ž[๐‘ฅ] =2๐‘ฅ

    1 โˆ’ 3๐‘ฅ

    Show that h(x) is a one to one function

    โ„Ž(๐‘ฅ) =2๐‘ฅ

    1 โˆ’ 3๐‘ฅ

    Let โ„Ž(๐‘ฅ1) = โ„Ž(๐‘ฅ2)

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    2๐‘ฅ11 โˆ’ 3๐‘ฅ1

    =2๐‘ฅ2

    1 โˆ’ 3๐‘ฅ2

    2๐‘ฅ1(1 โˆ’ 3๐‘ฅ2) = 2๐‘ฅ2(1 โˆ’ 3๐‘ฅ1)

    ๐‘ฅ1(1 โˆ’ 3๐‘ฅ2) = ๐‘ฅ2(1 โˆ’ 3๐‘ฅ1)

    ๐‘ฅ1 โˆ’ 3๐‘ฅ1๐‘ฅ2 = ๐‘ฅ2 โˆ’ 3๐‘ฅ1๐‘ฅ2

    ๐‘ฅ1 = ๐‘ฅ2

    ๐‘†๐‘–๐‘›๐‘๐‘’ ๐‘ฅ1 = ๐‘ฅ2, ๐‘กโ„Ž๐‘’๐‘Ÿ๐‘’๐‘“๐‘œ๐‘Ÿ๐‘’ โ„Ž(๐‘ฅ)๐‘–๐‘  ๐‘œ๐‘›๐‘’ ๐‘ก๐‘œ ๐‘œ๐‘›๐‘’ ๐‘“๐‘ข๐‘›๐‘๐‘ก๐‘–๐‘œ๐‘›

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    10. (a) Given ๐‘ƒ = [2 0 โˆ’4

    โˆ’1 6 2] , ๐‘„ = [

    โˆ’1 30 2

    โˆ’6 5] ๐‘Ž๐‘›๐‘‘ ๐‘… = [

    1 2 13 2 23 4 1

    ].

    Find ๐‘…โˆ’1 by using the elementary row operations method.

    Hence, if ๐‘…๐‘‹ = 3๐‘„ + ๐‘ƒ๐‘‡, determine the matrix ๐‘‹.

    (b) Ahmad bought an examination pad, 2 pens and a tube of liquid paper for RM18.

    Ali spent RM24 for 3 examination pads, 2 pens and 2 tubes of liquid paper. In

    the meantime Abu spent RM36 at the same store for 3 examination pads, 4

    pens and a tube of liquid paper. Let x, y and z represent the price per unit for

    examination pad, pen and tube of liquid paper respectively.

    i. Obatain the system of linear equations from the above information.

    ii. Write the system in the form of matrix equation ๐ด๐‘‹ = ๐ต.

    iii. State the price of each unit of examination pad, pen and tube of liquid

    paper.

    iv. Aminah bought 4 examination pads, 5 pens and 1 tube of liquid paper.

    What is the total price paid?

    SOLUTION

    a) ๐‘ƒ = [2 0 โˆ’4

    โˆ’1 6 2] , ๐‘„ = [

    โˆ’1 30 2

    โˆ’6 5] ๐‘Ž๐‘›๐‘‘ ๐‘… = [

    1 2 13 2 23 4 1

    ]

    (1 2 13 2 23 4 1

    |1 0 00 1 00 0 1

    )

    (1 2 10 4 13 4 1

    |1 0 03 โˆ’1 00 0 1

    )

    (1 2 10 4 10 2 2

    |1 0 03 โˆ’1 03 0 โˆ’1

    )

    ๐‘…2โˆ— = 3๐‘…1 โˆ’ ๐‘…2

    ๐‘…3โˆ— = 3๐‘…1 โˆ’ ๐‘…3

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    (

    1 2 1

    0 114

    0 2 โˆ’2

    |

    1 0 034 โˆ’

    14 0

    3 0 โˆ’1

    )

    (

    1 2 1

    0 114

    0 0 โˆ’32

    ||

    1 0 034

    โˆ’14

    0

    โˆ’32

    โˆ’12

    1)

    (

    1 2 1

    0 114

    0 0 1

    ||

    1 0 034 โˆ’

    14 0

    113 โˆ’

    23)

    (

    1 2 10 1 00 0 1

    ||

    1 0 012 โˆ’

    13

    16

    113 โˆ’

    23)

    (

    1 2 0

    0 1 00 0 1

    |

    |

    0 โˆ’13

    23

    12 โˆ’

    13

    16

    113 โˆ’

    23)

    (

    1 0 0

    0 1 00 0 1

    ||

    โˆ’113

    13

    12

    โˆ’13

    16

    113 โˆ’

    23)

    ๐‘…โˆ’1 =

    [ โˆ’1

    1

    3

    1

    31

    2โˆ’

    1

    3

    1

    6

    11

    3โˆ’

    2

    3]

    ๐‘…๐‘‹ = 3๐‘„ + ๐‘ƒ๐‘‡

    ๐‘…โˆ’1๐‘…๐‘‹ = ๐‘…โˆ’1(3๐‘„ + ๐‘ƒ๐‘‡)

    ๐‘‹ = ๐‘…โˆ’1(3๐‘„ + ๐‘ƒ๐‘‡)

    ๐‘…2โˆ— =

    1

    4๐‘…2

    ๐‘…3โˆ— = 2๐‘…2 โˆ’ ๐‘…3

    ๐‘…3โˆ— = โˆ’

    2

    3๐‘…3

    ๐‘…2โˆ— = ๐‘…2 โˆ’

    1

    4๐‘…3

    ๐‘…1โˆ— = ๐‘…1 โˆ’ ๐‘…3

    ๐‘…1โˆ— = ๐‘…1 โˆ’ 2๐‘…2

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    =

    [ โˆ’1

    1

    3

    1

    31

    2โˆ’

    1

    3

    1

    6

    11

    3โˆ’

    2

    3]

    [3 [โˆ’1 30 2

    โˆ’6 5] + ([

    2 0 โˆ’4โˆ’1 6 2

    ])๐‘‡

    ]

    =

    [ โˆ’1

    1

    3

    1

    31

    2โˆ’

    1

    3

    1

    6

    11

    3โˆ’

    2

    3]

    [[โˆ’3 90 6

    โˆ’18 15] + [

    2 โˆ’10 6

    โˆ’4 2]]

    =

    [ โˆ’1

    1

    3

    1

    31

    2โˆ’

    1

    3

    1

    6

    11

    3โˆ’

    2

    3]

    [โˆ’1 80 12

    โˆ’22 17]

    =

    [ (โˆ’1)(โˆ’1) + (

    1

    3) (0) + (

    1

    3) (โˆ’22) (โˆ’1)(8) + (

    1

    3) (12) + (

    1

    3) (17)

    (1

    2) (โˆ’1) + (โˆ’

    1

    3) (0) + (

    1

    6) (โˆ’22) (

    1

    2) (8) + (โˆ’

    1

    3) (12) + (

    1

    6) (17)

    (1)(โˆ’1) + (1

    3) (0) + (โˆ’

    2

    3) (โˆ’22) (1)(8) + (

    1

    3) (12) + (โˆ’

    2

    3) (17) ]

    =

    [ 1 + 0 โˆ’

    22

    3โˆ’8 +

    12

    3+

    17

    3

    โˆ’1

    2+ 0 โˆ’

    22

    64 โˆ’ 4 +

    17

    6

    โˆ’1 + 0 +44

    38 + 4 โˆ’

    34

    3 ]

    =

    [ โˆ’

    19

    3

    5

    3

    โˆ’25

    6

    17

    641

    3

    2

    3 ]

    bi) ๐‘ฅ + 2๐‘ฆ + ๐‘ง = 18

    3๐‘ฅ + 2๐‘ฆ + 2๐‘ง = 24

    3๐‘ฅ + 4๐‘ฆ + ๐‘ง = 36

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    bii) [1 2 13 2 23 4 1

    ] [๐‘ฅ๐‘ฆ๐‘ง] = [

    182436

    ]

    biii) ๐ด๐‘‹ = ๐ต

    ๐ดโˆ’1๐ด๐‘‹ = ๐ดโˆ’1๐ต

    ๐‘‹ = ๐ดโˆ’1๐ต

    =

    [ โˆ’1

    1

    3

    1

    31

    2โˆ’

    1

    3

    1

    6

    11

    3โˆ’

    2

    3]

    [182436

    ]

    =

    [ (โˆ’1)(18) + (

    1

    3) (24) + (

    1

    3) (36)

    (1

    2) (18) + (โˆ’

    1

    3) (24) + (

    1

    6) (36)

    (1)(18) + (1

    3) (24) + (โˆ’

    2

    3) (36) ]

    = [โˆ’18 + 8 + 12

    9 โˆ’ 8 + 618 + 8 โˆ’ 24

    ]

    = [272]

    ๐‘ฌ๐’™๐’‚๐’Ž ๐’‘๐’‚๐’… = ๐‘น๐‘ด๐Ÿ, ๐‘ท๐’†๐’ = ๐‘น๐‘ด๐Ÿ•, ๐‘ณ๐’Š๐’’๐’–๐’Š๐’… ๐’‘๐’‚๐’‘๐’†๐’“ = ๐‘น๐‘ด๐Ÿ

    biv) ๐‘ฅ โˆ’ ๐ธ๐‘ฅ๐‘Ž๐‘š๐‘๐‘Ž๐‘‘; ๐‘ฆ โˆ’ ๐‘ƒ๐‘’๐‘›; ๐‘ง โˆ’ ๐ฟ๐‘–๐‘ž๐‘ข๐‘–๐‘‘ ๐‘ƒ๐‘Ž๐‘๐‘’๐‘Ÿ

    ๐‘‡๐‘œ๐‘ก๐‘Ž๐‘™ ๐‘๐‘Ÿ๐‘–๐‘๐‘’ = 4(2) + 5(7) + 1(2)

    = 8 + 35 + 2

    = ๐‘…๐‘€45.00