符合题意的直线为y-12=k(x-5)得：y=k(x-5)+12圆x平方+y平方=9外一点P（5,12）引直线交圆于A,B两点.所以：x^2+y^2=9x^2+[k(x-5)+12]^2=9联立两方程得：x^2+k^2*x^2-10k^2*x+24kx+25k^2+144-9=0(k^2+1)x^2-(10k^2-24k)...