Can Someone please help me with this Math homework? Please respond ASAP

What is the volume of the sphere shown below with a radius of 3?

[10 points, algebra 2-simplifying complex fractions]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Will give let f(x)=2x and g(x)=[tex]2^{x}[/tex] graph the functions on the same coordinate plane. what are the solutions to the equation f(x)=g(x) ? enter your answers in the boxes x=[? ] or x=[? ]