x^3+y^2-5=7,则2x^3+2y^2+4=?

若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 3x+5y-(x+y)=6 2(x+y)-3x=-7 若3x-5y=0,则x+y/x=（）,x-y/y=（）,2x-3y/2x+3y=( ) x+y=1 5x-2y=8 3x-y=7 2x-y=3x表示y和用y表示x 已知方程组{(X+Y)-3(X-Y)=7,2(X+Y)+(X-Y）=-7}则(X+Y)(X-Y)= x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 化简:3(x-y)²-7(x-y)+ 2(x-y)²+5(x-y) (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 计算(x^8-x^7y+x^5y^3-x^4y^4+x^3y^5-x^y^7+y^8)(x^2+xy+y^2) 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 化简3(x-y)-7(x--y)+2(y-x) 化简:5(x-y)+2(x+y)-3(x-y)