solve this---**Extracted Content:** **Question 1:** * **Question Stem:** 一动圆与圆 $x^2+y^2+6x+5=0$ 外切，同时与圆 $x^2+y^2-6x-91=0$ 内切，则动圆圆心 $M$ 的轨迹方程是____. * **Mathematical Formulas:** * Circle 1: $x^2+y^2+6x+5=0$ * Circle 2: $x^2+y^2-6x-91=0$ * **Key Terms:** * 动圆 (moving circle) * 外切 (externally tangent) * 内切 (internally tangent) * 动圆圆心 $M$ (center M of the moving circle) * 轨迹方程 (locus equation) * **Options:** No options are provided in the image; it is a fill-in-the-blank question. * **Chart/Diagram:** No chart or diagram is present in the image.