(x3+y3)2-9x2y2(x+y)2 =[(x+y)-3xy(x+y)][(x+y)+3xy(x+y)] =(x+y)(1-3xy)(1+3xy)
﹙x³＋y³﹚²-3²x²y²﹙x+y﹚²＝﹙x³＋y³＋3x²y+3xy²﹚﹙x³+y³-3x²y-3xy²﹚＝x^6-16x³y³+9x^4y²-9x²y^4
