m^2/9+2mn/3+n^2=(1/9)(m^2+6mn+9n^2)=(1/9)(m+3n)^2a^2-14ab+49b^2=(a-7b)^216a^4+24a^2b^2+9b^4=(4a^2+3b^2)^2(x+y)^2-10(x+y)+25=[(x+y)-5]^2=(x+y-5)^22ab-a^2-b^2=-(a^2-2ab+b^2)=-(a-b)^24xy^2-4x^2y-y^3=-y(4...