## anonymous one year ago Thanks!

1. Michele_Laino

we have to apply this formula: $\Large \frac{{f\left( 7 \right) - f\left( 4 \right)}}{{7 - 4}}$

2. anonymous

$\frac{ f(3) }{ 3}$ So it would be?

3. Michele_Laino

no, you have to substitute the expression of your function, like below: $\large \begin{gathered} \frac{{f\left( 7 \right) - f\left( 4 \right)}}{{7 - 4}} = \hfill \\ \hfill \\ = \frac{{\left( {2 \times {7^2} - 16 \times 7 + 57} \right) - \left( {2 \times {4^2} - 16 \times 4 + 57} \right)}}{3} \hfill \\ \end{gathered}$

4. anonymous

Would the average rate of change be 6?

5. anonymous

So I had to plug in 4 and 4 into the original equation, then subtract them from each other and divide it by 3?

6. anonymous

I meant plug in 7 and 4

7. Michele_Laino

you have to plug in 7 and 4, so, the next step is: $\large \begin{gathered} \frac{{f\left( 7 \right) - f\left( 4 \right)}}{{7 - 4}} = \hfill \\ \hfill \\ = \frac{{\left( {2 \times {7^2} - 16 \times 7 + 57} \right) - \left( {2 \times {4^2} - 16 \times 4 + 57} \right)}}{3} = \hfill \\ \hfill \\ = \frac{{ - 14 + 32}}{3} = ...? \hfill \\ \end{gathered}$

8. anonymous

$\frac{ 18 }{ 3}$ Then simplified to 6?

9. Michele_Laino

that's right!

10. anonymous

Thank you!!

11. Michele_Laino

:)