(2x - 5)^2 can be expressed as (2x - 5) * (2x - 5) or simply just (2x - 5)(2x - 5)
Then multiply each term in the first parentheses against the all the other terms in the second parentheses.
(2x - 5)(2x - 5) = 4x^2 -10x - 10x + 25
Combine like terms.
4x^2 -10x - 10x + 25 = 4x^2 - 20x + 25
So, 4x^2 - 20x + 25 is the answer.