x＋y=15,250x＋80 y=2900.

x＋y=15,250x＋80 y=2900. x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 题目；X＋X+X+Y+Y=45,X+X+Y+y=34那么X是多少?Y是多少?x与Y的积是多少? 化简 x / y(x+y) - y / x(x+y) = 先化简,再求值:[(x＋y)(x-y)-(x-y)²+2y(x+y)]除4y,其中x=2,y=1 x＋x+x－y-y＝60 y+y+y-x-x=10 那么x=? y=? x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 X＋Y=240 X=Y＋Y＋Y X=?Y=?X＋Y=240 X=Y＋Y＋Y X=?Y=? /x/=3 /y/=4求x＋y x＋1.3=y-1.2,x（）y 把6x（x－y）的平方＋3（y－x）的立方分解因式我知道答案是6x(x-y)^2+3(y-x)^3=6x(x-y)^2-3(x-y)^3=3(x-y)^2[2x-(x-y)]=3(x-y)^2(x+y)可为什么=6x(x-y)^2-3(x-y)^3=3(x-y)^2[2x-(x-y)] 1.（－2a）³·b²÷(8a³b²) 2.－5x（2x²－3x＋4）+4x³+15x3.（x²-2y²）(x+2y)-2xy(x-y)4.（x-y+z）(x-y-z)化简求值 ［（x+y）(x-y)-(x+y)²-2y(x-2y)］÷(-2y),其中x=5,y=2003 x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? x=15y y=x(x x+y=80 5x+2.5y≤290 1.5x+3.5y≤212 2（x+y)-3(x-y)=3 ,4(x+y)+3(x-y)=15