Discrete Math Induction Proof Help With Question

I currently have to do this following proof using induction
(base case, inductive hypothesis required)

$$\sum_{i=1}^n(6i-3)=3n^2, \forall n>1$$

I'm not really sure how to approach this question and currently i've ended up with

$$=\frac{6n^2 - 5n}{2}$$ for the summation and don't really know where to go from here(or if that's even correct). Any help about where to go from here or what I did wrong is greatly appreciated! Thank you.