a.
h(x)=3*5ˣ; h(0)=3, h(1)=15: rate of change is (15-3)/1=12 (1st section)
h(2)=3*25=75, h(3)=3*125=375: rate of change (375-75)/1=300 (2nd section)
b.
So the second section is 300/12=25 times greater than the first section.
The function is exponential and as x gets larger the difference between consecutive values of h(x) increases dramatically so the rate of change increases.