Question 310901
4x^2 * 4x^3

This is actually

4*x*x*4*x*x*x

x is multiplied 5 times = x^5
4*4 = 16
Answer = 16 x^5
..

By following the indices rule 
you have to multiply the co-efficients and add the indices of the same terms

= 16x^(2+3)
16^5