设A（x1,y1),B(x2,y2)则x1^2 - 4y1^2 = 4 x2^2 - 4y2^2 = 4相减：（x1+x2）（x1-x2）＝4（y1+y2）(y1-y2)因为p(8,1)是AB中点所以x1+x2=16,y1+y2=2所以16(x1-x2)=4*2*(y1-y2)直线AB斜率：k=(y1-y2)/(x1-x2)=2AB:y-1=2(x-8)y=2x-15
