What is the area enclosed by the region defined by the equation $x^2+y^2+12x+16y=0$?
We can start by completing the square for the x's and y's respectively. So for the x's we have $(x+6)^2=x^2+12x+36$. Right. And that equals $(x+6)^2$. Now we'll do the y's. We have $y^2+16y=y^2+16y+64$. That's true. So we have $x^2+12x+36+y^2+16y+64=0+36+64$. Right. Now we can rewrite that as $(x+6)^2+(y+8)^2=100$. This is the equation of a circle with center $(-6,-8)$ and radius 10. So the area enclosed by the region is equal to the area of the circle, which is $\pi r^2$. That's true. So the area is $100\pi$.

