Answer:
Split up the integral.
â«(-6 to 0) [2 + sqrt(36 - x^2)] dx
= â«(-6 to 0) 2 dx + â«(-6 to 0) sqrt(36 - x^2) dx.
The first integral represents the area of a rectangle with base length 6 and height 2.
==> â«(-6 to 0) 2 dx = 6 * 2 = 12.
The second integral you figured correctly to be (1/4) π * 6^2 = 9π.
So, the final answer is 12 + 9Ď€.