若2x-3y=5,则6-4x+6y=急!~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

若2x-3y=5,则6-4x+6y=急!~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 若5x+3y=3x+4y=x+2y+6,则x+y=___ 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 若x+y=3,则x²-y²+6y=急 若X-3Y=2,则7-2Y+6Y=多少?急 几道 数学题急啊 对了再加20分(x+y)^2-(x+y)^3(x-y)^2-(x-y)^3 (x-y)^2-(y-x)^32(x-y)-3(y-x)^24ab(a+b)^2-6a^2b(a+b)(x+y)(x-y)-(x+y)^28a(x-y)^2-4b(y-x)a=-5 a+b+c=-5.2求代数式a^2(-b-c)-3.2a(c+b)的值 x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 （x+y）/2- x-y/2=6 3(x+y)=4(x-y) x+y/3+x-y/2=6 4(x+y)-2(x-y)=40 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 若x+y:y+z:z+x=3:4:5,则x:y:z=?(急,) 已知：2x=3y 则3x立方++4xde 平方y-5xy平方-y立方/x立方-2x平方y-5xy平方+6y立方就要啦 急 若|3/2 x-6|+|1/5+2y|=0,则x乘y二次方=?急