Question

Complete the square to rewrite y = -x2 + 8x - 7

Answer 1

x = 1 or x = 7

Explanation:

-x² + 8x - 7

= -(x² - 8x) - 7

= - [(x - 4)² - 16] - 7

= -(x - 4)² + 16 - 7

= -(x - 4)² + 9.

-(x - 4)² + 9 = 0

-(x - 4)² = -9

(x - 4)² = 9

x - 4 = ±√9

x - 4 = ±3

x = 3 + 4 or x = -3 + 4

x = 7 or x = 1