What is the width of the casing?

Question

The largest telescope in the world is on Mount Semirodriki. The diameter of its mirror is 6 m. The area of the mirror is equal to the cross-sectional area of the metal casing surrounding the mirror. What is the width of the casing?
The mirror is circular and contained in a circular casing.

Must use quadratic formula 

Answer 1

Draw and label of diagram!

w represents the width of the casing

The area of the mirror and the casing

(6 + w)²

The area of the mirror 9π

The area of the casing 9π

9π + 9π = (6 + w)²

 

Can you solve for w?