The function f is defined by f(x) = x^2 - 2x - 24. If f(x+3) = x^2 - kx - 21, what is the value of k?

k = 4

Step-by-step explanation:

In the equation: x² - 2x - 24

Replace the x with x + 3

(x+3)² - 2(x+3) - 24

x² + 6x + 9 - 2x - 6 -24

Let's rearrange it

x² + 6x -2x - 24 + 9 - 6

x² - 4x - 21

f(x+3) = x² - 4x - 21

it has to be a.