Calculate the average rate of change of the function f(x) = 3x2 over the interval 1 ≤ x ≤ 5. a) 4 b) 18 c) 36 d) 48

We have that
f(x) = 3x²   over the interval 1 ≤ x ≤ 5

for x=1
f(1)=3*1²> f(1)=3

for x=5
f(5)=3*5²> f(5)=75

[the average rate of change]=[f(5)-f(1)]/[5-1]> [75-3]/[4]---> 18

the answer is
18