The Laguerre polynomials are given by the explicit formula

Recall that the coeﬃcients of the Laguerre polynomials can be calculated using the recurrence relation;

,

For ﬁxed n use induction to prove the above summation formula.

I'm not too sure how to approach this question whether its through dummy variables or telescopic sums or whatever.

Help would be much be appreciated. Thank you