填空-5/7x=( )/7x=5/( ) x-y/x+y=X^2-y^2/( )

填空-5/7x=( )/7x=5/( ) x-y/x+y=X^2-y^2/( ) 解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y 5x+2y=83x-y=7 x+y=3 x+2y=9 3/x+1=y y-x=3 y=2x-3 y-3x=1 2(x+1)-y=6 7x-5y=-9 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 7x-3y/5=5x-y/3-x+y/2 x-1/5=y+1/3 方程2分之x+y+2分之x-y=7,4(x+y)-5(x-y)=2