Respuesta :

Answer:

x = 7 or -6

Step-by-step explanation:

Let a number be x.

Its square = x²

x - x² = 42

-x² + x - 42 = 0

-(x² - x + 42) = 0

x² - x + 42 = 0

(x - 7)(x + 6) = 0

x - 7 = 0 or x + 6 = 0

x = 7 or x = -6