$ S_1 \equiv x^2 + y^2 -4x+6y -23 = 0$ $ S_2 \equiv x^2 + y^2 -4x+6y -59 = 0 $ Are two circles. $P(8,-9)$ is a point in $S_2$. The tangents are drawn from $P$ to $S_1$ and the points of contact are $M$ and $N$. If the length of the line segment $MN$ is $x$, obtain $x^2$$-$ $70$
