SOLUTION: PLEASE HELP ME WITH THIS PROBLEM; fIND ALL ROOTS OF THE POLYNOMIAL X^3 - X^2 + 16X - 16

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Question 54470This question is from textbook ALGEBRA AND TRIGONOMETRY
: PLEASE HELP ME WITH THIS PROBLEM;
fIND ALL ROOTS OF THE POLYNOMIAL X^3 - X^2 + 16X - 16
This question is from textbook ALGEBRA AND TRIGONOMETRY

Answer by Edwin McCravy(20056)   (Show Source): You can put this solution on YOUR website!
PLEASE HELP ME WITH THIS PROBLEM;
fIND ALL ROOTS OF THE POLYNOMIAL X^3 - X^2 + 16X - 16

x³ - x² + 16x - 16

Factor x² out of the first two terms
Factor 16 out of the last two terms

x²(x - 1) + 16(x - 1)

Factor (x - 1) of of these two terms

(x - 1)(x² + 16)

+16 can be written as -16i²

(x - 1)(x² - 16i²)

The second parenthetical expression
is the difference of two squares, and
can be factored thusly

(x - 1)(x - 4i)(x + 4i)

Setting x - 1 = 0 gives 1 as one zero (root).
Setting x - 4i = 0 gives 4i as another zero (root).
Setting x + 4i = 0 gives -4i as the third zero (root).

Edwin


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