Respuesta :

thwng

Answer -7

Step-by-step explanation:

0 = x^2 + 4x - 21

0 = x^2 - 3x + 7x - 21

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

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

Therefore x - 3 = 0 or x + 7 = 0

so x = 3 or x = -7

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