Question

If x – 4 is a factor of x2 + 8x + k, what is the value of k?

Answer 1

The answer is

k=−11

Step-by-step explanation:

Let

f(x)=x^3−6x62+kx+10

If (x+2)is a factor

Then,

f(-2)=0

f(−2)= −8− 24 − 2k + 10= 0

2k=-22

k=−11

Step-by-step explanation:

Answer 2

k ±16

Step-by-step explanation:

Evaluate x^2 + 8 x + k where x = -4:

x^2 + 8 x + k = k - 4 8 + (-4)^2

(-4)^2 = 16:

k - 4 8 + 16

8 (-4) = -32:

k + -32 + 16

Grouping like terms, k - 32 + 16 = k + (16 - 32):

k + (16 - 32)

16 - 32 = -16:

Answer: k ±16