Answer:
D
Step-by-step explanation:
7x² - 56x = 63 ( divide through by 7 )
x² - 8x = 9
To complete the square
add ( half the coefficient of the x- term )² to both sides
x² + 2(- 4)x + 16 = 9 + 16
(x - 4)² = 25 ( take square root of both sides )
x - 4 = ± [tex]\sqrt{25}[/tex] = ± 5 ( add 4 to both sides )
x = 4 ± 5
Then
x = 4 - 5 = - 1
x = 4 + 5 = 9
solutions are (- 1, 9 ) → D
