Find the volume of the solid bounded by the cylinders and

I get however this is incorrect.

Let's solve for r. x2 + y2 = 16 r2 Step 1: Flip the equation. 16 r2 = x2 + y2 Step 2: Divide both sides by 16. 16 r2 16 = x2 + y2 16 r2 = 116 x2 + 116 y2 Step 3: Take square root. r = 116 x2 + 116 y2 or r = - 116 x2 + 116 y2 Answer: r = 116 x2 + 116 y2 or r = - 116 x2 + 116 y2