Find the maximum value |r| and any zeros of r. r=20-20 sin theta... r=0 is incorrect

What is best way to getting answer for my exam is

F(x) = x2 − 9, and g(x) = x − 3 f(x) = x2 − 4x + 3, and g(x) = x − 3 f(x) = x2 + 4x − 5, and g(x) = x − 1 f(x) = x2 − 16, and g(x) = x − 4 h(x) = x + 5 arrowright h(x) = x + 3 arrowright h(x) = x + 4 arrowright h(x) = x − 1 arrowright

Can someone check if i did this correct. it’s number 4 if you’re wondering.