Respuesta :

Step-by-step explanation:

x² - x - 20 = 0

x² - (5-4) x - 20 = 0

x² - 5x + 4x -20 = 0

x ( x - 5) + 4 ( x - 5) = 0

(x - 5) (x+ 4) = 0

Either.

x - 5 = 0

x = 5

Or,

x + 4 = 0

x = -4

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