先化简,在求值2x²-y²+(2y²-x²)-(x²+2y²
先化简,在求值:(x-y)²+(3x-2y)(2x+y)-x(6x-y)
先化简,后求值[(x-y)²-(x+y)]/(2xy) 先化简,后求值[(x-y)²-(x+y)]/
先化简在求值(x+y)²-(x-y)(x+y)-(xy)²÷(xy),其中x,y是方程组『3x+2y
先化简,再求值:(3x-y)²+(3x+y)(3x-y),其中x=1,y=-2
先化简在求值【(2y-3x)(-3x-2y)-(-3x+y)²-2y/3(3x-y+3xy²)】÷(
先化简,再求值,[x²+y²-(x-y)²+2y(x-y)]÷4y.其中x,y满足x
先化简,在求值[(x-2y)²-(x-y)(3x+y)-5y²]÷(-2x),其中x=
先化简,再求值.已知x=-2,y=125分之一,求x(3x-2y)+(2x+y)²+(2x-y)(x+y)-3
化简求值:x-y/x²-2xy+y²-xy+y²/x²-y²,其中(x
先化简再求值:(x-2y)²-(x+2y)(x-2y)-(x-3y)(x-y).其中x²+9y
化简求值 【2x²-(x+y)(x-y)][(x+y-1)(x-y+1)+1-2y],其中x=-1,y=-2
先化简,再求值:x²/x-y-y²/x-y,其中x=1+2又根号3