Answer:
x = 3 ± 2

Explanation:
x² - 6x = 15
to complete the square on the left side
add ( half the coefficient of the x- term )² to both sides
x² + 2(- 3)x + 9 = 15 + 9
(x - 3)² = 24 ( take square root of both sides )
x - 3 = ±
= ±
= ± (
×
) = ± 2

add 3 to both sides
x = 3 ± 2

then
x = 3 - 2
, x = 3 + 2
