x^2/9+y^2/4=1设A,B坐标分别是(x1,y1),(x2,y2),则有x1+x2=2,y1+y2=2有:x1^2/9+y1^2/4=1,x2^2/9+y2^2/4=1二式相减得:(x1+x2)(x1-x2)/9+(y1-y2)(y1+y2)/4=02(x1-x2)/9+2(y1-y2)/4=0AB的斜率是k=(y1-y2)/(x1-x2)=-4/9即...