Answer:
x²-10x+25
Explanation:
expand the expression
(x-5)²
(x-5)(x-5) distribute
x²-5x-5x+25
combine like terms
x²-10x+25
if you get x^2-25 then you're only squaring the x and 5, you have to square the whole equation (x-5)(x-5) is doing (x-5)^2. for example, if you just had (5)^2 you would take the whole "equation" which is 5 and times that equation by itself.