Question

Use the Midpoint Rule to approximate the integral (x^4) from 0 to 4 with n=0

Answer 1

n cannot be zero.
In any case, divide the interval into n equal pieces of width 4/n
then the midpoint of the kth interval (k=1..n) is
x_{_k} = 1/2 (4/n) + k*4/n
the area is then
n
∑ x_{_k}^4 * (4/k)
k=1

Answer 2

oops.
x_{_k} = 1/2 (4/n) + (k-1)*4/n