(-3a-4b)的2次幂=9a^2+24ab+16b^2(5x-2y)的2次幂+20xy=25x^2-20xy+4y^2+20xy=25x^2+4y^2[(2m+n)(2m-n)]的2次幂=[4m^2-n^2]^2=16m^4-8m^2n^2+n^4(y+3)的2次幂-(3-y)的2次幂=(y+3+3-y)(y+3-3+y)=2y*6=12y...