3x²+2xy-4y²-(3xy-4y²+3x²)
3x²y+xy²-[2xy²-4x²y+(x²y-2xy²)
(3x+2y)(9x²-6xy+4y²﹚
3x²y-﹛xy-[3xy-(4xy²+½xy)]-4x²y﹜
计算 2xy[4x²y²-3y(xy+x²y)-xy²]
(2x²y-3xy²)-3(x²y-2xy²)+2(x²y-4xy
2x²-5x+x²+4x-3x² -3x²y+2xy²+3xy
-3(xy-2x²)-[y²-(5xy-4x²)+2xy]
先化简,再求值 4(xy²+3xy-2x²y)-[12xy-3(3x²y-2xy²
2x²y+{2xy-[x²y-2(﹣3x²y+xy)]﹣4xy²} 计算
化简4xy-3y²-3x²+xy-3xy-2x²+x²-2y²
化简求值:4xy-(2x²+5xy-y²)+2(x²+3xy),其中x=负2,y=二分之一
已知x²-xy=4,y²-xy=9求下面代数式的值(1)x²-2xy+y²;(2