若｜x｜=2.5,｜y｜=7/3,求x+y.

若x,y为正整数,且满足3x(x+y)-y(x+y)=7,求x,y 用递归法求y=x-(x*x*x/3!)+(x*x*x*x*x/5!)-(x*x*x*x*x*x*x/7!)+. 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 若x-y=2(x+y),求代数式x-y/x+y+x+y/x-y求代数式 x+y分之x-y+x-y分之x+y 已知:y=ax的3次方+bx+3,当x=-1/2时,y=-7,试求x=1/2时,y的值 若x、y满足2x+y=6,x-3y=1,求7y(x-3y)²-2(3y-x)³的值 已知:3x-5y=0,求x/y,x-y/y,x-y/x 若(-x+6):(x-y):(4x+y)=3:14:1,求x+y 若(-x+6):(x-y):(4x+y)=3:14:1,求x+y 若｜x｜=2.5,｜y｜=7/3,求x+y. 若实数X,Y同时满足3x+2y=7和2x+3y=3,求x+y/x-y X:2.5=Y:3/4 求X:Y 急 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) x+2.5-y=7-y 求未知数X y+x+13.2=18+y 求未知数X 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 1 已知x+y/y=7/3 求x+y/x-y等于什么2 若x+4/3=y+3/2=z+8/4 且x+y+z=12 求x、y、z的值 x-y=3 7-x+y-y平方+X平方已知x-y=3 求代数式7-X+y-(y-x)²的值 已知（x+y）2 =2,(x-y)3 =3,求(x+y)7(x-y)2(x+y)3(y-x)4 的值 21/(x+y)+4/(x-y)=12/(x+y)+7/(x-y)结果为(x+y)/(x-y)=3求过程!