+0

# Last hard to understand polynomial question for today

0
82
1
+172

Could I get help on one more?

What are the zeros of the polynomial function?

f(x)=x4+2x3−16x2−2x+15

Options

−5

−1

0

1

3

5

Nov 8, 2018

#1
+3617
+1

$$x^4+2x^3 -16x^2 -2x+15 =\\ (x^4-16x^2+15) + (2x^3-2x)= \\ (x^2-15)(x^2-1) + 2x(x^2-1) = \\ (x^2+2x-15)(x^2-1) = \\ (x+5)(x-3)(x-1)(x+1) \\ \\ \text{zeros are read off as }\\ x=-5,~3,~1,~-1$$

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Nov 8, 2018