The given equation is expressed as
x^2 = 12x + 25
x^2 - 12x = 25
We would add the square of half thecoefficient of x to both sides of the equation
The coefficient of x is - 12
half of the coefficient of x is -6
The square of 6 is - 6^2 = 36
It becomes
x^2 - 12x + (-6)^2 = 25 + 36
(x - 6)^2 = 61
Taking square root of both sides of the equation, it becomes