若2^x=6,4^y=5则2^x-2y

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 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y* 若x/y=4/3 则3x+2y/2x-5y= 若3x-5y=0,则x+y/x=（）,x-y/y=（）,2x-3y/2x+3y=( ) {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 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