3x-2y=5 3x+2y=12 则9x的平方-4y的平方等于多少

4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 5x=3y,(2x+y)的平方=5x(x+y)+9 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 3x-2y=9 x-3y=2 x+y=5 x+2y=3 y=x 2x+y=8 3y=2x y/3=x/2 12/x=9/y y/x=?y/x=?x/y=? 若3x-5y=0,则x+y/x=（）,x-y/y=（）,2x-3y/2x+3y=( ) 若2x=3y,则(x*x+y*y)/x*x=? 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 若x-2y=5,则式子12-x+2y=.以知3x-4y=2x+y则x∶y= 12y(x-y)^2-8(x-y)^3=? (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)=