Factored form x2-15x+36
[tex] x^{2} -15x+36

I hope this helps you

x^2-15x+36

x -3

x -12

(x-12)(x-3)

You're basically looking for the form (x-a)(x-b)

This is because in your equation, the coefficient x (-15) is negative but the constant, 36 is positive.

So when you expand (x-a)(x-b) you get:

x$^2$ - ax - bx + ab which is the same as:
x$^2$ - (a - b)x + ab. If we compare the coefficients in that to the equation
x$^2$ - 15x + 36 

you will see that we need two numbers such that
-a-b=-15 and
a*b=36

The two numbers are 12 and 3

So x$^2$ - 15x + 36=(x-12)(x-3)