已知x/y=3/5.则在(1)(x-y)/(x+y)=1/4(2)(x+3)/(y+5)=3/5(3)x/(x+2y)=
已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-(
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
已知:3x=8y.求(1)x+y/y (2)2x+3y/x-2y
先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y
已知x+y+2(-x-y+1)=3(1-y-x)-4(y+x-1),则x+y等于( )
(1)已知x+y=6,x²-y²=5,求x-y的值(2)若x+y=3,x²+y²
化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1
若3x-5y=0,则x+y/x=(),x-y/y=(),2x-3y/2x+3y=( )
已知实数x满足x+1/x=3,求x-1/x的值 如果x平方+y平方-4x-2y+5=0,则(根号x)+y/(根号x)-y
已知x=3分之1,y=二分之一,求代数式x-(x+y)+(x+2y)-(x+3y)+...-(x+13y)的值
10/x+y+3/x-y=-5 15/x+y-2/x-y=-1(用换元法解此方程组)
设函数y=y(x)满足微分方程y″-3y′+2y=2e^x 且曲线y=y(x)在(0.1)处与已知曲线y=x^4-x+1