Question

Fpr whta value of k,(x+5) os a factor of p(x)=-x^3+x+3k?

Answer 1

x=-5 is zero of polynomial
then
-x^3+x+3k=0
if x=-5
-(-5)^3+(-5)+3k=0
125-5+3k=0
120+3k=0
3k=-120
k=-120/3
k=-40

Answer 2

The correct answer is -40.

Given: The equation = $-x^{3}+x+3k.$.

Factor of equation = x+5.

To Find: The value of k.

Solution:

If (x+5) is a factor of $-x^{3}+x+3k$ then it should satisfy the equation.

Put -5 in place of x in the equation.

0 = $-(-5)^{3} +(-5)+3k$

0 = -(-125) - 5 + 3k

0 = 125-5+3k

-3k = 120

k = -40

Hence, the value of k is -40.

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