y-x/7-x+y/6=1/2 5(x+y)-2(y-x)=1怎么解答

{6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 初二上学期方程题 4x+y=5 5x+4y=63x-2y=1 2x+3y=13x-2y=7 7x+5y=32x+3y=17 2x-y=-4x+5y=6 2x+y=23x-6y=4 3x+2y=52x+y=73x-4y=53x+y=1x-2y=-1x+y=42x+3y=92x-3y=74x+5y=3x+y=20004x+6y=90003x+5y=113x-2y=42x+3y=215x-2y=5x+y=54x+3y=182x+3y=16x+4y=132x+3y=40x y-x/7-x+y/6=1/2 5(x+y)-2(y-x)=1怎么解答 解方程组6(x-y)-7(x+y)=21 2(x-y)-5(x+y)=-1 6（x-y)-7(xy)=21,2(x-y)-5(x+y)=-1 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 1、(-y^3)^5/y^3/ y^2+2(-y)^102、(x-y)^7/(y-x)^6+(x+y)^3/(x+y)^23、已知X^a=5,x^b=3,求X^(3a-2b)的值 3x+5y-(x+y)=6 2(x+y)-3x=-7 x+y=1 5x-2y=8 3x-y=7 2x-y=3x表示y和用y表示x 例X=1 y=21.X+Y=5 X-Y=15 2.2X+3Y=4 5X+6Y=7 3.X+3Y=5 3X+Y=-1 4.2X+Y=3 3X+5Y=11 5.4X+3Y=6 2X+Y=4 6.X+Y=180 X=3Y-10 7.3X-2Y=3 2X-Y=7 8.5X+3Y=7Y X+Y=45 9.3X+4Y=126X+8Y=24 X:6Y=1:4 10.X+Y=138 X-45=Y+53 11.X+Y=60 14Y=20X 12.2X+3Y=15.5 5X+6Y=35 13.X+Y=170 3 {x+y=1 ,xy=-6{x(2x-3)=0,y=x²-1{(3x+4y-3)(3x+4y+3)=0,3x+2y=5{(x-y+2)(x+y)=0,x²+y²=8{(x+y)((x+y-1)=0,(x-y)(x-y-1)=0 把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)= 3(x-y)把(x-y)看作一个整体,化解:5(x-y)+2(x-y)-4(x-y)=3(x-y)²-4(x-y)+7(x-y)-6(x-y)²= (x+y)/6+(x-y)/10=1,(x+y)/6-(x-y)/10=5 解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7 x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 x+2y=2x+y+1=7x-y 求：2x-y? 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于