Question

When factored, the trinomials x2 + 4x − 21 and x2 + 11x + 28 have one binomial factor in common. What is this factor?

x − 7
x + 7
x − 5
x + 5

Answer 1

x + 7

Explanation:

x2 + 4x − 21

set equal to 0

x2 + 4x − 21 = 0

factor

(x - 3) (x + 7)

x2 + 11x + 28

set equal to 0

x2 + 11x + 28 = 0

factor

(x + 4) (x + 7)