Test series

Question

Can anyone solve this recurrence relation T(n) = 3T(n-1) + O(n^2)

Its ans is O(3^n n^2)

Comments

applying masters theorem for decreasing function may also give the required result.
for a > 1,
T(n) = O (a^(n/b) * f(n)) or O (a^(n/b) * nk )
T(n) = O (3^(n/1)*n^2)

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@Abhrajyoti00, Interestingly, here $T(n)= \Theta(3^n)$. Terms with $n^2 3^n$ and $n3^n$ will be cancelled when you solve the whole equation which you had written. I have edited and solved the summation which you are finding difficult. 

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Thank You So Much @ankitgupta.1729 Sir.