(x+5)(x-5)
= x^2 - 5x + 5x - 25
= x^2 - 25
(5x+3)(5x-3)
= 25x^2 - 15x + 15x - 9
= 25x^2 - 9
do you see the pattern? both the coefficient on x and constant multiply together to make a perfect square and the middle term, also known as "b" term cancels out leaving a binomial