If 4x^2-100=0, the roots are

This is a difference of 2 perfect squares where you can factor x^2-y^2=(x-y)(x+y) so

also if it is equal to zero and you factor, then each factor is assumed set to zero exg
xy=0 then assume x and/or y=0 so

4x^2-100
(2x)^2-(10)^2=(2x-10)(2x+10)=0
so the roots are (2x-10) and (2x+10)
(solution is 5 and -5)