practice problems on functions (maths)
TRANSCRIPT
1
CPP: FUNCTIONS(1) Find the domain of the following functions.
1. ( ) 2f x x 1 x= − −
2. ( ) 1f x
x x=
−
3. ( ) ( )310 10log log 1f x x= +
4. ( ) ln lnf x x=
5. ( ) ( )1 24cos log x
f x e−
=
6. ( ) [ ]( )lnf x x x= − , [.] = G.I.F.
7. 2 2 2x y+ =
8. ( )2
1 21sin 1
2
xf x x
x− += + −
9. ( ) [ ]( )1sinf x x x−= + , [.] = G.I.F.
10. ( ) ( )2
1 12
1 xf x sin log x cos(sinx) cos
2x− − += + +
11. ( ) ( )10
12
log 1f x x
x= + +
−
12. ( ) ( )22
log 3
3 2
xf x
x x
+=
+ +
13. ( ) 1f x sin 2x6
− π= +
14. ( ) ( )2
1
4
sin 2
xf x
x−
−=−
15. ( ) ( )( )210 10log 1 log 5 16f x x x= − − +
16. ( ) ( )0.32
log 1
3 18
xf x
x x
−=
− −
17. ( ) 1
2
xf x
x
−=
−
18. ( )2
10
5log
4
x xf x
−=
19. ( ) 11
1 2cos log
3 x
xf x x−
−
−= +
20. ( ) ( )24 5 3log log log 18 77f x x x= − −
21. ( ) 10
1log
sinf x
x=
22. ( ) [ ]1, . . . .
1 7 6f x G I F
x x= = − + − −
23. ( ) [ ]1, . . . .
1 5f x G I F
x= =
− −
24. ( ) ( )1 2 2 1 !35cos
12
xf x x
x x− +
= − + +
, [.] =
G.I.F.
25. ( ) 10100
2log 1log x
xf x
x
+ = −
26. ( )12 9 4
1
1f x
x x x x=
− + − +
27. ( ) 7
3x
xf x P−−=
28. ( ) 10 10 10 10log log log logf x x=
29. ( ) 0.4
1log
5
xf x
x
− = +
30. ( ) [ ]1 2sec 1 , .f x x x− = − + = G.I.F.
31. ( ) ( )2 1log
xf x x
−=
2
32. ( ) { }logxf x x= , {.} = fractional part
33. ( ) 1 2sin 2 3 ,f x x− = − [.] = G.I.F.
34. ( ) ( )1 3 1
cos2 ln 4
xf x
x− −
= + −
35. ( ) [ ]log ,xf x x= [.] = G.I.F.
36. ( ) 1 22
1sin log
2f x x− =
37. ( )[ ] [ ]
[ ]2
1, .
6f x
x x= =
− −G.I.F.
38. ( ) 3 1 12 5
1log log 1 1f x
x
= − + −
39. ( ) ( )2
22
loglog
3 4 log
xf x
x
= −
40. ( ) 1 1cos
sinf x
x−=
ANSWERS
1. 1
,12
2. ( ),0−∞ 3. (0, ∞) 4. (0, 1) ∪ (1, ∞)
5. 1 1
2, ,22 2
− − ∪ 6. R – I 7. (-∞, 1) 8. {-1, 1}
9. [0, 1) 10. {1} 11. [-2, 1) – {0} 12. ( ) { }3, 2, 1− ∞ − − −
13. 1 1
,4 2
− 14. [ )1,2 15. ( )2,3 16. [ )2,6
17. ( ) [ ] ( ), 2 1,1 2,−∞ − ∪ − ∪ ∞ 18. [ ]1,4 19. ( ) ( )0,1 1,2∪ 20. ( )8,10
21. { }|R n n Zπ− ∈ 22. ( ] { } [ ){ }0,1 2,3,4,5,6 7,8R − ∪ ∪ 23. ( ] [ ), 7 7,−∞ − ∪ ∞
24. 1
2 −
25. 1 1 1
0, ,100 100 10
∪ 26. R
27. { }3,4,5 28. ( )1010 ,∞ 29. ( )1,∞ 30. ( ] [ ),0 1,−∞ ∪ ∞
31. ( )2,∞ 32. ( )0,1 33. [ ] { }1,1 0− −
34. [ ] [ ) ( )5, 1 1,3 3,4− − ∪ ∪ 35. [ )2,∞ 36. [ ] [ ]2, 1 1,2− − ∪ 37. ( ) [ ), 2 4,−∞ − ∪ ∞
38. ( )0,1 39. [ )8,16 40. ( )2 1 , 2
n n Zπ+ ∈
3
CPP: FUNCTIONS(2) Find the range of the following functions.
1. ( ) 22
1
1f x x
x= +
+
2. ( ) 2f x 9 x= −
3. ( ) 1
2 cos3f x
x=
−
4. ( ) 21
xf x
x=
+
5. ( )2
23sin16
f x xπ= −
6. ( ) 7
3x
xf x P−−=
7. ( ) 1 1 1sin cos tanf x x x x− − −= + +
8. ( )2
2
x x 2f x
x x 1
+ +=+ +
9. ( ) ( )210log 3 4 5f x x x= − +
10. ( ) ( )23log 5 4f x x x= + −
11. ( ) 2
sin cos 3 2log
2
x xf x
− +=
12. ( ) 2 4sin cosf x x x= +
13. ( ) ( )1 2cot 2f x x x−= −
14. ( ) [ ][ ] ,
1
x xf x
x x
−=
− + [.] = G.I.F.
15. ( ) , 0x x
x x
e ef x x
e e
−
−
−= >+
16. ( ) 1 5f x x x= − + −
17. ( ) 1f x
1 2cos x=
−
18. ( )2
12
xf x cos
1 x−
= +
19. ( ) ( )1 2f x sin x x 1−= + +
20. ( ) 1 2 3f x x x x= − + − + −
21. ( ) 1 2f x x x= − − +
22. ( ) cos2 sin 281 27x xf x =
23. ( ) 4 2 1x xf x = − +
24. ( )2
2 2
x xf x
x x
−=+
25. ( ) 5
3
xf x
x=
+
26. ( )2
293sin
16f x x
π= −
1. [1, ∞) 2. [0, 3] 3. 1
,13
4. 1 1
,2 2
−
5. 3
0,2
6. { }1,2,3 7. 3
,4 4
π π
8. 7
1,3
9. 10
11log ,
3 ∞
10. (-∞, 2] 11. [ ]1,2 12. 3
,14
13. ,4
π π
14. 1
0,2
15. ( )0,1 16. 2,2 2
4
17. ( ] 1, 1 ,
3 −∞ − ∪ ∞
18. 0,2
π
19. ,3 2
π π
20. [ )2,∞
21. [ ]0,3 22. 55
1,3
3
23. 3
,4 ∞
24. 1
,12
R − −
25. ( )5,5− 26. [ ]0,3
Even/Odd Functions
1. ( ) ( )2af x log x 1 x , a 0, a 1= + + > ≠
2. ( )x
x
a 1f x x
a 1
+= −
3. ( ) x
x xf x 1
e 1 2= + +
−
4. ( ) ( )12 tan2
xf x eπ−= −
5. Let [ ]: 10,10f R− → , where
( )2
sin ,x
f x xa
= +
[.] = G.I.F. be an odd
function. Find the values of ‘a’.
6. Draw the graph of the following function and decide whether it is even or odd.
x | x |, x 1
f (x) [1 x] [1 x] 1 x 1
x | x |, x 1
≤ −= + + − − < <− ≥
, where
[.] = G.I.F.
7. If a function f satisfies
( ) ( ) 0f x f x a+ + = for all real x and
0,a > prove that the function is periodic. Also, find its period.
8. Let :f R R→ be a function given by
( ) ( ) ( ) ( )2f x y f x y f x f y+ + − = for all
real ,x y . If ( )0 0,f ≠ prove that f is an
even function. If ( )0 0,f = prove that f
is an odd function.
1. Odd 2. Even 3. Even 4. Odd 5. (100, ∞) 6. Even 7. 2a Periodic Functions 1. ( ) ( ) ( )cos sin cos cosf x x x= +
2. ( ) 2 3sin tan sin tan2 2 2
x x xf x x= + + + +K
1sin tan2 2n n
x x−+ +
3. ( ) | sin x cos x |f x
| sin x | | cos x |
+=+
4. ( ) [ ] cos cos2 cosx x x x n xf x e π π π− + + + += K , [.] =
G.I.F.
5. ( ) ( )sin cosf x x x= +
6. ( ) ( )cos sin cosf x x x= −
7. ( ) [ ]tan ,2
f x xπ =
[.] = G.I.F.
8. ( ) 3sin sin 3f x x x=
9. ( ) ( )1 sin
cos 1 cos
xf x
x ecx
+=+
10. For what value of ‘a’ are the functions sin cosax ax+ and sin cosx x+ periodic
with the same period?
1. 2
π 2. 2n π 3. π 4. 1
5. 2π 6. 2
π 7. 2 8. π
9. π 10. a = 4
5
CPP: FUNCTIONS(3) One-One/Many-One/Onto/Into Functions 1. : ,f R R→ ( ) 3 26 11 6f x x x x= − + −
2. : ,f R R→ ( ) 2 sinf x x x= +
3. [ ) [ ): 0, 0, ,f ∞ → ∞ ( )1
xf x
x=
+
4. : ,f R R→ ( ) 3 2 3 sinf x x x x x= + + +
5. : ,f R R→ ( )2
2
4
1
xf x
x
−=+
6. : ,f R R→ ( )2
2
x 4x 30f x
x 8x 18
+ +=− +
7. : ,f N N→ ( ) ( )1x
f x x= − −
8. : ,f R R→ ( ) 4 4xxf x = +
9. : ,f R R→ ( ) 2f x x x= +
10. [ ] [ ]: 1,1 1,1 ,f − → − ( )f x x x=
11. { } { }: 3 1 ,f R R− → − ( ) 2
3
xf x
x
+=−
12. : ,f R R→ ( ) 0, x rationalf x
x, x irrational
∈= ∈
: ,g R R→ ( ) 0, x irrationalg x
x, x rational
∈= ∈
Then ( ) ( )f g x− is ...
13. Which of the following functions from Z to itself is a bijection?
(a) ( ) 3f x x= + (b) ( ) 5f x x=
(c) ( ) 3 2f x x= + (d) ( ) 2f x x x= +
14. Which of the following functions is one-one?
(a) ( ) 2 2, f x x x R= + ∈
(b) ( ) [ )2 , 2,f x x x= + ∈ − ∞
(c) ( ) ( ) ( )4 5 , f x x x x R= − − ∈
(d) ( ) { }2
2
4 3 5, , ,
4 3 5
x xf x x R
x xα β+ −= ∈ −
+ −
where ,α β are the roots of the equation 24 3 5 0.x x+ − =
15. If the function : ,f A B→
( ) 2 6 8f x x x= − + − is bijective, find the
maximum interval for B. 16. Find the number of bijective functions
from a set A to itself when A contains 100 elements.
17. Find the number of surjections from
{ }1,2,3, ,A n= K onto { }, .B a b=
18. Set A has 3 elements and set B has 4 elements. Find the number of injections that can be defined from A to B.
19. Find two distinct linear functions which map [-1, 1] onto [0, 2].
20. If : ,f R R→ ( ) sinf x px x= + is one-one
and onto, find the interval in which p lies. 21. Let f be a one-one function with domain
{ }, ,x y z and range { }1,2,3 such that
exactly one of the following statements is true and the rest are false:
( ) ( ) ( )1, 1, 2.f x f y f z= ≠ ≠ Find the
value of ( )1 1 .f −
22. Find the interval of values of a for which the function :f R R→ defined by
( ) ( )3 24 6 6f x x a x ax= + + + + is one-one.
23. Find the interval of values of a for which the function :f R R→ defined by
( )2
2
6 8
6 8
ax xf x
a x x
+ −=+ −
is onto.
1. Many-one and Onto 2. One-one and Onto 3. One-one and Into 4. One-one and Onto 5. Many-one and Into 6. Many-one and Into 7. One-one and Onto 8. Many-one and Into 9. Many-one and Into 10. One-one and Onto 11. One-one and Onto 12. One-one and Onto 13. (a) 14. (b) 15. ( ],1B = −∞ 16. 100!
17. 2 2n − 18. 24 19. 1x + and 1 x− 20. ( )1,1R − −
21. y 22. [ ]2,8a ∈ 23. [ ]2,14a ∈
6
Inverse Function 1. Find the inverse of the function
( ) , 0, 1.x x
x x
a af x a a
a a
−
−
−= > ≠+
2. Let [ ) [ ): 4, 1,f ∞ → ∞ be defined by
( ) ( )45 .x xf x −= Find ( )1 .f x−
3. Let ( ] ( ]: ,2 ,4f −∞ → −∞ be defined by
( ) 24 .f x x x= − Find ( )1 .f x−
4. Let [ ) [ ): 1, 2,f ∞ → ∞ be defined by
( ) 1.f x x
x= + Find ( )1 .f x−
5. Let 1 3
f : , ,2 4 ∞ → ∞
be defined by
( ) 2 1.f x x x= − + Find the inverse of
( )f x if it exists. Hence or otherwise,
solve the equation 21 3
1 .2 4
x x x− + = + −
6. Find the values of the parameter a for which the function ( ) 1f x ax= + is the
inverse of itself. 7. Let :f R R→ be a function given by
( ) , .f x ax b x R= + ∈ Find ‘a’ and ‘b’ such
that ( ) .fof x I=
8. If ( ) 2
, 1
, 1 4,
8 , 4
x x
f x x x
x x
<
= ≤ ≤ >
find ( )1 .f x−
9. Let :f X Y→ be defined by
( ) sin cos .4
f x a x b x cπ = + + +
If f is
bijective, find X and .Y 10. If ( ) ( ) ( )3 / 2 1, ,xf x x e g x f x−= + = find
the value of ( )' 1 .g
1. ( )1 1 1log
2 1a
xf x
x− + = −
2. 52 4 log x+ + 3. 2 4 x− − 4. 2 4
2
x x+ −
5. ( )1 1 3f x x
2 4− = + − , x = 1 6. 1a = − 7. 1, 0a b= = or 1, a b R= − ∈
8. ( )1
2
, 1
, 1 16
, 1664
x x
f x x x
xx
−
<= ≤ ≤ >
9. [ ], , , ,2 2
X Y c r c rπ πα α = − − − = − +
where
1 2tan
a b
aα − +=
and 2 2 2r a b ab= + +
10. 2 Composite Functions
1. If ( ) x 1, x 1f x ,
2x 1, 1 x 2
+ ≤= + < ≤
( )2x , 1 x 2
g x ,x 2, 2 x 3
− ≤ <= + ≤ ≤
find ( )fog x
and ( ) .gof x
2. If ( ) 1 1 , 1 3f x x x= − + − − ≤ ≤ and
( ) 2 1 , 2 2g x x x= − + − ≤ ≤ , find
( )fog x and ( ) .gof x
3. If ( ) 2
2 , 1
2 1, 1
x xf x
x x
<= − ≥
and
( ) 2, 0,
2 , 0
x xg x
x x
+ <= ≥
find ( ).fog x
4. If ( ) 1 , 0 2,
3 , 2 3
x xf x
x x
+ ≤ ≤= − < ≤
find ( ) .fof x
5. If ( ) , 1,
2 , 1
x xf x
x x
≤=
− > find ( ) .fof x
7
6. Let f be a function defined on [ ]2,2−
and given by ( ) 1, 2 0
1, 0 2
xf x
x x
− − ≤ ≤= − < ≤
and ( ) ( ) ( ) .g x f x f x= + Find ( ) .g x
7. If ( ) [ ]1 , 3,3 ,f x x x= − ∈ − find the
domain of ( ) .fof x
8. If ( ) 2f x x= − and ( ) 1 2 ,g x x= − find
the domain of ( ).fog x
1. ( )2
2
x 1, 1 x 1fog x ,
2x 1, 1 x 2
+ − ≤ ≤= + < ≤
( ) ( )2gof x x 1 , 2 x 1= + − ≤ ≤
2. ( )1, 2 1
1, 1 0
1, 0 2
x x
fog x x x
x x
+ − ≤ < −= − − − ≤ ≤ − < ≤
, ( ) 1 , 1 1
3 , 1 3
x xgof x
x x
+ − ≤ ≤= − < ≤
3. ( )
2
2
2 4, 1
2 8 7, 1 0
14 , 0
21
8 1, 2
x x
x x x
fog x x x
x x
+ < − + + − ≤ <= ≤ <
− ≥
4. ( )2 , 0 1
2 , 1 2
4 , 2 3
x x
fof x x x
x x
+ ≤ ≤= − < ≤ − < ≤
5. ( )2 , 1
, 1 1
2 , 1
x x
fof x x x
x x
− < −
= − ≤ ≤ − >
6. ( ), 2 0
0, 0 1
2 2, 1 2
x x
g x x
x x
− − ≤ <= ≤ < − ≤ ≤
7. [ ]2,3− 8. 3 1
,2 2
−
Functional Equations
1. If 22
1 1, 0,f x x x
x x + = + ≠
prove that
( ) 2 2, 2.f x x x= − ≥
2. If ( ) ( )cos ln ,f x x= find the value of
( ) ( ) ( )1.
2
xf x f y f f xy
y
− +
3. ( )f x is a polynomial function satisfying
( ) ( )1 1,f x f f x f
x x = +
{ }0x R∈ −
and ( )3 28.f = Find ( )4 .f
4. g is a function satisfying
( ) ( ) ( ) ( ) ( ) 2g x g y g x g y g xy= + + − for
all real ,x y and ( )2 5.g = Find ( )5 .g
5. If ( ) , 0,x
x
af x a
a a= >
+ prove that
( ) ( )1 1.f x f x+ − = Also, find the value of
1 2 1996.
1997 1997 1997f f f + + +
K
2. 0 3. 65 4. 26 5. 998
8
Miscellaneous 1. The function ( )f x is defined for [ ]0,1 .x ∈ Find the domain of (i) ( )2 3f x + , (ii) ( )tanf x , and (iii)
( )sin .f x
2. Solve for x : { } [ ] [ ]6 2 5 3 .x x x x+ + + = +
3. f is an even function defined on ( )5,5− . Find the real values of x satisfying ( ) 1.
2
xf x f
x
+ = +
4. The function ( )f x satisfies ( ) ( ) ( )( ) ( )( )( )1
2 3 31 2 3 3f x p f x f x f x+ = + − + − for all real x and
0p > is a constant. Prove that f is periodic and find its period.
5. The function ( )f x satisfies ( ) ( ) ( )1 1 3f x f x f x+ + − = for all real x . Prove that the function is
periodic and find its period.
6. The function ( )f x satisfies the relation ( ) 1 15, 0, .af x bf x a b
x x + = − ≠ ≠
Find ( )f x .
7. The function ( ),f x y satisfies the relation ( )2 , 2 .f x y x y xy+ − = Find ( ), .f x y
8. If ( ) ( ) ( )f x y f x f y+ = for , ,x y N∈ ( )1 2f = and ( ) ( )1
16 2 1n
n
k
f a k=
+ = −∑ , find the value of .a
1. (i) 3
, 12
− − (ii) ,
4n n
ππ π + (iii) ( )2 , 2 1n nπ π + 2.
12
3
3. 1 5 3 5
,2 2
− ± − ± 4. 2p 5. 12
6. ( ) 2 2
1 5af x bx
a b x a b = − − − +
7. ( )2 2
,8
x yf x y
−= 8. 3a =
Number of solutions 1. Find the number of solutions of
( )sin sin sinx y x y+ = + and 1.x y+ =
2. Solve for x: 2
3 40.
3 4
x x
x x
−≥
− −
3. Solve for x: ( )1 1 2 .x x xe e e+ − = −
4. cos2 sin ,x x= [ ]2 ,5x π π∈ −
5. sin lnx xπ =
6. 7 5x x− = −
1. 6 2. ( ) [ ), 1 0,4x ∈ −∞ − ∪ 3. ln 3x = 4. 14
5. 6 6. 4