Get equation for velocity of a satellite

[rcrx]

Derive an equation for the velocity around Earth. Satellite has no mass. Radius not given. Only period, G, and ME (earth)

G = 6.67X10^-11 nm^2/kg^2 | Earth = 5.98x10^24 kg | Period = T = 1.20x10^4s

I know I can find radius, and then find velocity. But I am supposed to derive an equation to suit the given information.

Homework Equations

V = √GM/r
V = 2πr / T

The Attempt at a Solution

I'm not positive about my ability to cut r from the equations and merge them?

 

[Rake-MC]

You say that you know that you can solve for radius and then find velocity, but you're supposed to derive an equation to suit the given information.

Well, solving for radius and then velocity is in a way doing what they asked, except just don't solve for r numerically!

Re arrange one of the equations so it's r = [...] and then put the [...] in as r for the other equation.