1. The problem statement, all variables and given/known data (i) Combine Equations A and B to give a single equation for v and substitute this in place of v in Equation C. (ii) Rearrange your answer to part (i) to make r the subject of the equation. 2. Relevant equations Equation A z = Δλ/λ0 Equation B v = zc For a planet such as the one orbiting Gliese, the speed v is linked to the mass of the star M and the planet’s orbital radius, by Equation C: Equation C v2 = GM/r G is Newton’s universal constant of gravitation. 3. The attempt at a solution (i) v = (Δλ/λ0)c -> (Δλ/λ0)c2 = GM/r (ii) this is where I'm not sure, is the above correct? I always get roots confused.