Calculating the scale factor (cosmology) for a universe starting at the Big Bang

[Hangst]

Homework Statement

Show that by using the Friedmann-equation you can determine the scale factor for a Universe in it's early stages (starting with the Big Bang) to:

Homework Equations

The equation for the scale factor:

Where r(t) is the distance from us to a given galaxy to the time t and r0 is the galaxies current distance from us.And the Friedmann equation:

The Attempt at a Solution

I'm dumbfounded and I have no idea of what to do. This is for a major paper and any help is much appreciated. If you don't understand the problem, please do say so and I'll try and clear it up. Thanks a lot!

 

[Hangst]

Here is my thinking so far: isolate the scale factor so that you have:

and then find values for the two unknowns somehow.

 

[Hangst]

Here is my thinking so far: isolate the scale factor so that you have:

and then find values for the two unknowns somehow.

Doesn't matter anymore, figured it out. You can lock this now.