letM(x1,y1),N(x2,y2)ax+by+c=0 (1)x^2+y^2=9 (2)sub (1) into (2)x^2+[(-ax-c)/b]^2 =9b^2x^2 + a^2x^2+2acx+c^2=9b^2(b^2+a^2)x^2+2acx+c^2-9b^2=0x1x2=(c^2-9b^2)/(b^2+a^2)similarly[(-by-c)/a]^2 +y^2 =9(a^2+b...