With this equation, you'd distribute one set of parenthesis into the other. Doing so you'd get "X^2 - 1x - 5x + 5 = 0". Simplified, you'd have "X^2 - 6x + 5 = 0"
Next, you'd find the factors of 5, that when multiplied equal 5, and when added, equal -6. Being that 5 is a prime number (a number that is only divisible by 1 and itself) those numbers are 1 and 5. Both numbers have to be negative, in order to get -6.
-1*-5 = 5
-1 + -5 = -6
Finally you split up the X^2 to a single x with each of the factors and make it equal to zero (X - 1 = 0) and (X - 5 = 0). Then you solve each.
(X - 1 = 0) Add 1 to each side. X = 1
(X - 5 = 0) Add 5 to each side. X = 5
I hope this helps!
