do now: find all real zeros of the function.. academy algebra ii 5.7: apply the fundamental theorem...
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Do Now: Find all real zeros of the function.Do Now: Find all real zeros of the function.
42191852)( 234 xxxxxf
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Academy Algebra IIAcademy Algebra II
5.7: Apply the Fundamental 5.7: Apply the Fundamental
Theorem of AlgebraTheorem of Algebra
HW Friday: p.384 (12-18 even)HW Friday: p.384 (12-18 even)
Test 5.5-5.9: Tuesday, 12/2Test 5.5-5.9: Tuesday, 12/2
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Descartes’ Rule of SignsDescartes’ Rule of Signs• The number of positive real zeros of f is
equal to the number of sign changes in the sign of the coefficients of f(x) or is less than this by an even number.
• The number of negative real zeros of f is equal to the number of changes in sign of the coefficients of f(-x) or is less than this by an even number.
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Fundamental Theorem of AlgebraFundamental Theorem of Algebra
• If f(x) is a polynomial with degree of n (where n>0), then the equation f(x) = 0 has at least one solution.
• Corollary: The equation f(x) = 0 has exactly n solutions provided each solution repeated twice is counted as 2 solutions, each solution repeated three times is counted as 3 solutions, and so on.
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Fundamental Theorem of AlgebraFundamental Theorem of Algebra• Example: x3 – 5x2 – 8x + 48 = 0
(x+3)(x – 4)2= 0
x = -3 and x = 4
This equation only has two distinct solutions: -3 and 4. Because the factor (x – 4) appears twice, you can count the solution 4 twice. With the repeated solution the third-degree equation has three solutions.
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Solve the equation.Solve the equation.x3 + 5x2 + 4x + 20 = 0
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Find the zeros of the Find the zeros of the polynomial function.polynomial function.
f(x) = x4 – 8x3 + 18x2 – 27
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Find all zeros of the Find all zeros of the polynomial function.polynomial function.
f(x) = x5 – 2x4 + 8x2 – 13x + 6
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Conjugates TheoremConjugates Theorem• If is an imaginary zero of
function f, then is also a zero.• If is a zero of function f where
is irrational, then is also a zero. ba
ba b
bia bia
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Write a polynomial function f of least Write a polynomial function f of least degree that has rational coefficients, a degree that has rational coefficients, a
leading coefficient of 1, & the given zeros.leading coefficient of 1, & the given zeros.1.) -1, 2, 4
2.) 4, 51
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Write a polynomial function f of least Write a polynomial function f of least degree that has rational coefficients, a degree that has rational coefficients, a
leading coefficient of 1, & the given zeros.leading coefficient of 1, & the given zeros.3.) 2, 2i, 64