设A(X1,Y1),B(X2,Y2)因为M是AB的中则有X1+X2/2=1,Y1+Y2/2=1,中点定理把A,B两点代入椭圆方程.X1^2/4+Y1^2/3=1,X2^2/4+Y2^2/3=1两个式子相减得X1^2-X2^2/4+Y1^2-Y2^2/3=1(X1+X2)(X1-X2)/4+(Y1+Y2)(Y1-Y2)/3=0(X1+X2)(X...