Question

Find the roots of the quadratic equation x^2-8x=9 by completing the square. Show your work.

Answer 1

`x^(2) -8x=9 \\ x^(2) -8x+(-4)^(2) = 9 + (-4)^(2) \\ x^(2) -8x+16 = 9 + 16 \\ (x-4)^(2) =25 \\ x-4= √(25) \\ x-4= \pm 5 \\ x= \pm 5+4`
x = 5 + 4 or -5 + 4
x = 9 or -1