Pls help me on this equation

Show algebraically that f and g are inverse functions f(x)=x^2/-6; g(x)=square root of 2x+12

Find the length of the following tangent segments to the circles centered at o and o' whose radii are 5 and 3 respectively and the distance between o and o' is 12. what is the tangent segment of cd?

Tiffany drives 285,120 feet before lunch and 628,320 feet after lunch. about how many kilometers does she drive all together