Lambert(Guidance) Equation Derive (Velocity) from equations

[cemfrost]

Homework Statement

http://a1201.hizliresim.com/t/f/1sjw1.gif
http://a1201.hizliresim.com/t/f/1sjxk.gif

Homework Equations

http://d1201.hizliresim.com/t/f/1sjxx.gif

The Attempt at a Solution

http://c1201.hizliresim.com/t/f/1sk69.gif
I think there will be a mistake at solution and I can't find ? Help please ?
How can I derive last equation with using other equations..(This is the Lambert Velocity Problem)

 

[D H]

How can I derive last equation with using other equations..(This is the Lambert Velocity Problem)

Solve your equation (2) for λ, then use equation (1) to find v.

 

[cemfrost]

Thanks for help ;)