I figured 50% on my own. I believed it’s a half circle. Because if you plug in x= -2 and x= 2 you get 0. So those are two points. And when you plug in 0 you get 1. So I got confused, because now it’s not a circle. It’s an oval.

Then I googled it and cheated. But I’m still not sure how the person who solved it, got 2 from plugging in x = 0 to create a perfect circle.

Long story short, I tried to solve it, but couldn’t. Googled it, but still not convinced.