This trinomial is in a special form that can
be factored as the product of two binomials.
x² - 10x + 25
The first term in each binomial will be a factor of the x² term.
Since x² is just x · x, we use those as our first factors.
To factor this trinomial, we need factors of our constant that
add to the coefficient of the middle term in our trinomial.
So we're looking for factors of 25 that add to -10.
When your constant is positive and your middle term is negative,
you are going to use the negative factors of your constant term.
So the two numbers hat multiply to gives
us 25 and add to -10 are -5 and -5.
So our answer is (x - 5)(x - 5).