Find a:

(x+3)(x+a)(x+7)=x³+15x²+71x+105

a = 5

Step-by-step explanation:

(x+3)(x+a)(x+7)=x³+15x²+71x+105

(x+3)(x+a)(x+7) = (x²+10x+21)(x+a) = x³ + (10+a)x² + (21+10a)x + 21a

21a = 105

a = 5

check: 21 + 10a = 71   ... 71x

            10 + q = 15   15x²

5x+40

5(x + 8)

7x - 49

7(x - 7)

18x + 9

9(2x + 1)

15x - 10

5(3x - 2)

step-by-step explanation:

for number one all you have to do is factor 5 out of 5x + 40

for number 2 factor 7 out of 7x - 49

for number three factor 9 out of 18x + 9

for number four factor 5 out of 15x - 10

b

step-by-step explanation: