Question

Pls help u dont have to explain that much​

Answer 1

k = -7

Explanation:

Given

x² - x - 42 = (x + k)(x + 6)

Required

Find k

x² - x - 42 = (x + k)(x + 6)

Expand the left hand side

x²-7x + 6x - 42 = (x + k)(x+ 6)

Factorize

x(x - 7) + 6(x- 7) = (x + k)(x+ 6)

Further factorize

(x - 7)(x + 6) = (x + k)(x + 6)

By comparison

x + k = x - 7

Subtract x from both sides

k = -7