Question

Select the correct answer. Solve for x. x2 + 4x - 21 = 0 A. -3, -7 B. -3, 7 C. 3, -7 D. 3, 7

Answer 1

x= -7, 3

Explanation:

x^2 +4x-21=0

You need to extract the factors for the equation. Two factors that multiplied give the result -21 and added give +4, with the form:

x^2 +4x-21=0

(x+7)(x-3)=0

You obtain:

x+7=0

x=-7

and,

x-3=0

x=3

Answer 2

B

Explanation:

x² + 4x - 21 = 0 ← in standard form

(x + 7)(x - 3) = 0 ← in factored form

equate each factor to zero and solve for x

x + 7 = 0 ⇒ x = - 7

x - 3 = 0 ⇒ x = 3