Question 203051
X^2 - 6X = 16
Complete the square in the left
X^2 - 6X + 9 - 9 = 16
(X-3)^2 - 9 = 16
(X-3)^2 = 25
(X-3)^2 = 5^2

so
X-3 = 5   ===>  X = 8
or
X-3 = -5  ===>  X = -2

Answer :  X = -2 or 8