2(3xy-2x²-3y²)+3(x²-5xy+3y²)
3x²y+xy²-[2xy²-4x²y+(x²y-2xy²)
化简(3X²-XY+Y²)-5(X²-XY+2Y²)
计算 2xy[4x²y²-3y(xy+x²y)-xy²]
-2y³+(3xy²-x²y)-2(xy²-y³)
计算:(-7x²y)(2x²y-3xy³+xy)
-3(xy-2x²)-[y²-(5xy-4x²)+2xy]
计算:x²y-(2xy²-5x²y)+3xy²-y³
化简3/(x²+2xy+y²)-4/(x²-2xy+y²)+5/(x²
(2x²y-3xy²)-3(x²y-2xy²)+2(x²y-4xy
求3x²y-2xy²+2(xy-二分之三x²y)-xy+3xy²的值,其中x=3
先化简,再求值:{xy(x²-3y)+3xy²}(-2xy)+x³y²(2x-y
(xy-2y)(xy+2y)-(x-y)²-x²y² 其中x=5/2 y=- 3/5 先化