x^2-2x+1=24+1
(x-1)^2=25
x-1=5
x=5+1
x=6
Basically, to complete the square, take the number in the term -2x, divide by 2, and square it.
So:
(-2/2)^2=1
this is the number that has to be after -2x to complete the square
Add 1 to make x^2-2x into x^2-2x+1 (make sure to add 1 on the other side too), then solve for x