Question

Solve the quadratic equation. Simplify if possible:

-5 (x + 3) 2 = -80

Answer 1

Explanation:

(x +y)² = x² + 2xy +y²

-5(x + 3)² = -80

-5(x² + 2*x*3 + 3²) = -80

-5(x² + 6x + 9) = -80

Divide the equation by (-5)

x² + 6x +9 = -80/-5

x² + 6x + 9 = 16

x² + 6x + 9 - 16 = 0

x² + 6x - 7 = 0

x² - x + 7x - 7 = 0

x(x - 1) + 7(x - 1) = 0

(x - 1)(x + 7) = 0

x -1 = 0 ; x + 7 = 0

x = 1 ; x = -7