(x-1/2)^2=_____

题目

(x-1/2)^2=_____
(a+b)+_____=(a-b)^2
(2x-5)(5+2x)-(2x-5)^2=
我看见代数式就头疼,

答案

(x-1/2)^2=x^2-x+1/4
(a+b)^2+_(-4ab)____=(a-b)^2
(2x-5)(5+2x)-(2x-5)^2=(2x-5)(2x+5-2x+5)=10(2x-5)