1+2X=3+Y 5X=4Y的答案

{ (x+y)/5+(x-y)/2=3 (x+y)/5-(x-y)/2=1的答案是多少, 1+2X=3+Y 5X=4Y的答案 y=(x^2-4x-5)/(x^2-3x-4)的值域是答案是y≠1且y≠6/5怎么算的? 已知x-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 2元一次方程组的答案（1）2x+3y=40 (2)5x+2y=18 (3)7x+2y=11 y=2x y=-x x-y=-1 已知x,y∈R+,且1/x+4/y=1,求x+y的最小值x+y=x+x分之一+y+y分之4-1≥2+4-1=5,可是答案是9,为什么会错呢 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 (3x-4y)^2-(3x+y)^2(x+1/2y-3)(x-1/2y+3)已知x+y=5,X^2-Y^2=15,求x-y的值是 x加二分之一y减去3你们的答案我看不懂~好多不一样的%…… 先化简,再求值：[(2x+y)²-（2x-y)(2x+y)]÷（2y）,其中x=3,y=-1的答案 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-(x+2009y)的值. 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-(x+2009y)的值. 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 先化简,再求值[2x的平方-(x+y)(y-x)][3(-x-y)(y-x)+4y的平方]其中x=三分之一y=1 1:4(x-100)+3y=5 2:6(x-y)-2(x+y )=14 x-100=-y 3(x-y)+(x+y)=5 先无视上面的1.4(x-100)+3y=5x-100=-y2.6(x-y)-2(x+y )=143(x-y)+(x+y)=5 (x+2y)(x-2y)-(2x-y)的平方+(3x-y)(2x-5y)其中x=-1 y=13分之1 若x=-1/4,能否确定代数式(2x-y)(2x+y)+(2x-y)(y-4x)+2y(y-3x)的值? 已知(3x+1)(3x-3)-3x+2)^2=-7,(y+7)(y-7)-y(y-7)=0,求8y^2-5y(-y+3x)+4y(-4y-5/2x)的值