2x+3y=-1,4x-9y=8怎么做?
9y=3x-(x-1),4(x+y)-(2x+4)=8y
x=4-5y,3x-9y=4用代入法怎么做
y=3x平方+2x怎么做啊
化简(x+y)+(2x+1/2y)+(3x+2/3y)+(4x+3/4y)+...+(9x+8/9y)=?
{4/(x+y)+6/(x-y)=3 {9/(x-y)-1/(x+y)=1
已知4x=9y求(1)x+y/y (2)y-x/2x
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
(2x-3y)2-(4y-3x)(3x+4y)怎么做?
[(3x+y)²-(3x-y)²]÷(4x-2y)计算 怎么做?
2x-y=8 3x+2y=5与3x+2y=1 3x-4y=-11用加减法怎么算?
化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1
已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-(