1) (-2a+5b)(-a-2b)=(2a-5b)(a+2b) now cancel (a+2b) from numerator and denominator then you will get the final answer

2) hints

(a/b)x(b/c)=a/c [b get cancel from numerator and denominator]

(-2/xy)^2=4/(xy)^2

(y-x)^2=(x-y)^2 use this to cancel (x-y) from denominator and numerator