(1)18(m+n)²-2(m-n)² =16m^2+40mn+16n^2=8(2m^2+5mn+2n^2)=8(2m+n)(m+2n) (2)2y-3x-9x²+4y²= (4y^2+2y+ 1/4) -(9x^2+3x+1/4)=(2y+1/2)^2 -(3x+1/2)^2=(2y+3x+1)(2y-3x)