5. Evaluate the definite integral: $\int_{0}^{3} 16 x\left(x^{2}+1\right)^{3} d x$
The final answer is \(\boxed{19998}\).
Step 1 :Define the variable x.
Step 2 :Define the function as \(f = 16x(x^2 + 1)^3\).
Step 3 :Compute the definite integral of the function from 0 to 3.
Step 4 :The result of the definite integral from 0 to 3 of the function \(16x(x^2+1)^3\) is 19998.
Step 5 :The final answer is \(\boxed{19998}\).