apply master theorem T(n) = aT(n/b) +f(n)
a==8
b==2
f(n)=n2
nlogba==>nlog28====>nlog223===>n3
theorem says
1)if f(n) is polynomial time greater than nlogba then answer is ⊝ f(n)
2)if f(n) is polynomial time less nlogba then answer is nlogba
which is greater then n2 so...answer is ⊝ (n)3