圆x^2+y^2=1和圆x^2+y^2-6x-8y+9=0的公切线有

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 x+y=1 5x-2y=8 3x-y=7 2x-y=3x表示y和用y表示x 圆x^2+y^2=1,求点[(x(x+y),y(x+y)]的轨迹方程 两圆x^2+y^2-2x+4y+1=0和x^2+y^2+4x-2y+4=0的公切线有几条 动点P(x,y)在圆上x^2+(y-1)^2=1,求(y-1)/(x-2)的最大值和2x+y的最小值 动点P(x,y)在圆上x^2+(y-1)^2=1,求(y-1)/(x+2)的最大值和2x+y的最小值 (x-2y)(x+y)-2x(-2x-3y)+6x(-x-y),其中x=-1,y=2要讲解和答题 2x+4y=3 -3x-2y=1 ..求x和y 2x+y=1,25x+2y=-40,求x和y? (2x-2y)/3-(x-y)=-1和6(x+y)-4(2x-y)=16 2y(x+二分之一y)-[(x+y)(x-y)+2y(y+x)],其中|x-1|=2 （x-y)(x+y)-(x+y)^2+2y(y-x),其中x=1,y=3. 解方程组,(x+y)^2-3(x+y)=0和x-y=1 已知X和Y满足3X+4Y=2,X-Y-1/7 解方程组3(x+y)-4(x-y)=4和(x+y)/2+(x-y)/6=1kkkkkkkk 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 [(-x-y)(-x+y)-(x+y)^2-x(y-y^2)}÷1/2y