x÷3+y÷4=54 x÷5+y÷4=42 的解是什么?哥哥姐姐帮帮忙!

已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 已知x-2y=2011,求[(3x+2y)(3x-2y)-(x+2y)(5x-2y)]÷4x的值. 2x-y=2,求[(x²+y²)-(x-y)²+2y(x-y)]÷4y x²-4y² x+2y---------- ÷ --------分数线x²+2xy+y² x²+xyx²-4y² x+2y----------÷--------分数线x²+2xy+y² x²+xy(x+2y)(x-2y)x(x+y)=----------------(x+y)(x+y)(x+2y)(x-y)x=------(x+y)这样对了吗? 先化简,再求值:[(x+2y)²-(x+y)(3x-y)-5y²]÷2x,其中x=-4,y=-3. x²/xy-x/y 3x/4x+y - x-2y/4x+y (1-y/y+x)÷x/y²-x² 已知x²+4y²-4x+4y+5=0,求(2x-y)(x+y)/x四次方-y四次方×xy-y²/2x-y÷(y/x²+y²)² [(x+y)(x-y)-(x-y)²+2y(x-y)]÷4y [(x+2y)²-（x+y)(3x-y)-5y²]÷(2x),其中x,y满足x²+4x+y²-y+17/4=0已知、x+y=6且xy=4(1)x²+y² (2)（x-y）² (3)x{四次方}+y{四次方}第一题没错 书上就这样写的！ 一、 (x-y)^5÷(y-x)^2-(x-y) 二、 先化简,后求值 (2x-y)^13-[(2x-y)^3]-[(y-2x)^2]^4 其中x=2 y=-1 (X-Y)^8÷(Y-X)^4÷(X-Y)^3=-(X-Y)这个计算结果对吗? [x／（x-y）]·[y²／（x+y）]-[x^4y／（x^4-y^4）]÷[x²／（x²+y²）]= [(x+2y)(x-2y)-(x+4y)²]÷4,其中x=5,y=-2 【（x+2y)（x-2Y)-(x-2y)²】÷4Y,其中x=2,y=½ 已知x.x+y.y-4y+5=0,求（x-3y）÷（x+3y）得志 化简求值:[(x+y)(x-y)-(x-y)²+2y(x-y)]÷4y,其中x=二分之一,y=2 化简求值:[(x+y)(x-y)-(x-y)²+2y(x-y)]÷4y,其中x=二分之一,y=2 已知x=y+2,求[(x+y)(x-y)-(x-y)的2次方+2y(x-y)]÷4y的值