Time Complexity

Question

How to solve the following recurrence relation?

T(n) = T(n-6) + n² , n>7

T(n) = 1 , n<= 7

Comments

$O(n^3)$ ?

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using substitution method

you will get o(n³)

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@adarsh @goxul

i got T(n)=1+13²+19²+25²+............+n²

if it is right how to solve it further or if it is wrong then what is right ??

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$T(n) = T(n-6k) + \Sigma_{0}^{k-1} (n - i)^2$, $n -6k = 7$.

Just expand the summation and you should get a $n^3$ term there.