Verified answer

Explications étape par étape:

1)

(x + 5)² = (x+5)(x+5) = x² + 5x + 5x + 25 =

xź + 10x + 25.

2)

a) k = (x+5)² - 3(x+5)

b) k = (x+5) [x+5 -3) = (x+5)(x+2)