{x/2-y/5=4 x/5-y/15=3用代入法解方程组

x*x+2x+y*y-4y+5=0 x= y= 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 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 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 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*y)的值 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? x+2y=3（x+y）+5 3x-4y=4（x+y）-15 解方程x+y+(x+y/2)=15 3x+5y+4(x+y/2)=62 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 5x-4y(y-x)=? 化简求值：2(x+y)(x-2y)-2x(x+y),其中x、y满足x^2+y^2-2x+4y=-5 (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuaihuajian 3X=5Y （X+Y)*3X=(2Y+X)*4+2*2 x*x+y*y-2x+4y+5=0求x, 2x+y=4 x+2y=5 x+y等于?2x+y=4x+2y=5x+y等于? .先化简再求值：（2x+y）（2x+y)-(2x-y)平方其中X,Y满足X平方+Y平方-2X+4Y+5=0