Hello! :) Find the average rate of change in the function: f(x)=−3x2−x from x1=5 to x2=6

Question

Hello! :) Find the average rate of change in the function:  f(x)=−3x2−x from x1=5 to x2=6

mathmath333 · Answer

First find $f(x_1)=f(5)$ and $f(x_2)=f(6)$.

mathmath333 · Answer

$\large \color{black}{\begin{align} f(x)=−3x^2−x \hspace{.33em}\~\
 f(5)=−3(5)^2−5=-75-5=-80 \hspace{.33em}\~\
\end{align}}$

similarly find $f(6)$

melissa_something · Answer

Oh thanks for correcting my math mistake. Oh okay and after that just subtract? @mathmath333

mathmath333 · Answer

the formula would be 

$\text{The average rate of change }=\dfrac{f(6)-f(5)}{6-5}$

so just find the value of $f(5)$ and put it's value in the formula and get the answer.