Answer:
(x + 7)(x - 3)
Step-by-step explanation:
To factor the quadratic
Consider the factors of the constant term (- 21) which sum to give the coefficient of the x- term (+ 4 )
The factors are + 7 and - 3 since
+ 7 × - 3 = - 21 and + 7 - 3 = + 4, hence
x² + 4x - 21 = (x + 7)(x - 3)
