(3x^2-4x+1)(3x^2+4x+1)=[(3x^2+1)-4x][(3x^2+1)+4x]=(3x^2+1)^2-16x^2=9x^4+6x^2+1-16x^2=9x^4-10x^2+12(3-5a)^2-5(3a-7)(3a+7)=2(5a-3)^2-5(3a-7)(3a+7)=50a^2-60a+18-5(9a^2-49)=50a^2-60a+18-45a^2+245=50a^2-45...我就是这样做、可是老师打了个错。题目的类型就是化简~ 已知xy=8满足x^2y-xy^2-x+y=36.求x^2+y^2的值详细说下。x^2y-xy^2-x+y=36xy(x-y)-(x-y)=36(xy-1)(x-y)=36(8-1)(x-y)=367(x-y)=36x-y=36/7(x-y)^2=1296/49x^2+y^2-2xy=1296/49x^2+y^2-2*8=1296/49x^2+y^2-16=1296/49x^2+y^2=1296/49+16x^2+y^2=2080/49（xy-1)(x-y)=36（xy-1）怎样得的？xy(x-y)-(x-y)=36提取公因式 (x-y)(xy-1)(x-y)=36