x^2-12x+36
Now, the constant term will be divided such that the factors sum or difference is equal to the middle term (coefficient of x)
36= 3*12
= 3*2*6
= 6*6
Hence, the two factors of 36 i.e. 6 and 6 gives the sum = 12.
Thus, we can write,
x^2-12x+36
= x^2-6x-6x+36
Taking common, we get,
= x(x-6)-6(x-6)
=(x-6)(x-6)
Thus, the two factors are (x-6) and (x-6)