先化简再求值:【1/(x-y)-1/(x+y)】÷(xy²)/(x²-y²),其中x=1-
先化简再求值:【1/(x-y)-1/(x+y)】÷(xy²)/(x²-y²),其中x=1-
先化简,再求值,x分之x-y÷(x-x分之2xy-y²)其中x=2,y=-1
化简求值:(X×根号X+X×根号y)÷(XY-Y²)-(X+根号XY+Y)÷X×根号X-Y×根号Y,其中X=1
先化简再求值(3x²y-xy²)-3(x²y-2xy²)其中x=1/2,y=1/
再求值)x²-2x/2y-xy 其中x=-1,y=2
先化简,再求值:3x²—[2x²y—(xy—x²)]+4x²y,其中x=—1,y
(1/x-y+1/x+y)÷2x/x²+2xy+y².其中x=-2.化解求值.求步骤!急!
先化简再求值(x-y/1-x+y/1)÷x平方+2xy+y平方/2y,其中x=根号3+2,y=根号3
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:3(2X²Y-3XY²)-2(2XY²-3X²Y),其中X=1,Y=-
化简求值:[(x-2y)²-4 y+2xy]÷2x其中x=-1,y=2
化简求值[1-(2x/x+y)]÷ (x²-2xy+y²/3x+3y)+(x²+xy/x&