X+Y=290 4%x+5%y=13

（5x+3y)(3y-5x)-(4x-y)(4y+x)= 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 已知：4x = 5y,求(x+y) ：y x-y+5x-4x= ? 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y* 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( 数学题……555{(3x+y)(3x-y)-(x-5y)(5x-y)-(x-2y)²÷(-4x),x=-2.y 已知x²+y²+5=2x+4y,求【2x²-(x-y)(x-y)】【(x+y-1)(x-y x+y=5; x^y+y^x=17 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)