已知圆C:X^2+y^2-2x-2y+1=0相切的直线L交X轴,Y轴于A,B两点,|OA|=a,|OB|=b,(a>2,b>2).求证:(a-2)*(b-2)=2.求线段AB中点的轨迹方程,求三角形AOB面积的最小值.

已知集合A={y|y=(1/2)^x,x0}C.{y|y=2} 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 已知圆C:x^2+y^2-2x-2y+1=0,直线l:y=kx 已知XmolH2O中含有y个H2O分子,则阿弗加德罗常数为 A Y/X B 2Y/X C (X/Y)MOL-1 D (Y/X)MOL-1 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知x-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙 已知:【(x²+y²)-(x-y)²+2y(x-y)】/4y=1,求4x/4x²-y²-1/2x+y 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 已知圆x,y满足x^2+y^2 a(x-y)(x+y)-b(y-x)(x+y)-c(x-y)^2(y+x)提取公因式 已知x,y满足约束条件：x-y+1>=0,x+y-2>=0,x 已知抛物线y=1/2x²+x+c与y轴没有交点 已知A=3x^2-12,B=5x^2*y^3+10x*y^3,C=(x+1)(x+3)+1求其公因式已知A=3x*x-12,B=5x*x*y*y*y+10x*y*y*y,C=(x+1)(x+3)+1求其公因式,若无,说出理由 已知圆面C:(x-a)^2+y^2 已知x-y=3,求[（x+y)(x-y)-(x-y)^2+2y(x-y)]除以的值 已知3x =2y 求x/x+y+y/x-y-y²/x²-y² 已知x/y+z=y/x+z=z/x+y,分式(x+2y+3z)/(2x+5y-2c)有意义时的值