Question

(r+7)(r-4)

1. -4r² - 36r - 80

(m+9)(m-5)

1. -2n² - 24n - 40

Explanation:

Step1: Factor out -4 from expression 17

$-4(r^2 + 9r + 20)$

Step2: Factor the quadratic inside

Find two numbers that multiply to 20 and add to 9: 4 and 5.
$-4(r+4)(r+5)$

Step3: Factor out -2 from expression 18

$-2(n^2 + 12n + 20)$

Step4: Factor the quadratic inside

Find two numbers that multiply to 20 and add to 12: 2 and 10.
$-2(n+2)(n+10)$

Answer:

1. $\boldsymbol{-4(r+4)(r+5)}$
2. $\boldsymbol{-2(n+2)(n+10)}$