Find the average rate of change of x over the interval [1, 5]

For f(x) = x^3 + 2x, the average rate of change with respect to x over the interval [1, 5] is:
a) 18
b) 20.5
c) 24
d) 32.5
e) 33

f(x) = x^3 +2x.............(i)
f(5) = 5^3+2*5 =125 +10 =135
f(1) = 1^3+2*1 = 1+2 =3
f(5) -f(1) = 135 - 3 = 132
5-1 = 4
Hence rate change = 132/4 = 33 ..................Ans

The averagre rate of change is
[f(5)-f(1)]/[5-1]=[135-3]/4=132/4=33.