The average rate of change of function describes the average rate at which y-value ( or f(x)) is changing with respect to changing x-value.
The average rate of change=\(\frac{ y_{1}- y_{2} }{ x_{1} - x_{2} }\) In this exaple is x1=4 and x2=7 and we will find y1 and y2:
y1=3(4-3)²+4=31+4=7
y2=3(7-3)²+4=316+4=48+4=52
Finally:\(\frac{52-7}{7-4}= \frac{45}{3} =15\)
Answer: The average rate of change for f(x) from x=4 to x=7 is 15.