# Thread: average rate of change

1. ## average rate of change

Let
f(x)=5 ·x2+2 ·x−3 and let x0= 1.

The average rate of change of f between x= 1 and x= 1.18 equals ?

2. Originally Posted by samtheman17
Let
f(x)=5 ·x2+2 ·x−3 and let x0= 1.

The average rate of change of f between x= 1 and x= 1.18 equals ?

$f(x) = 5x^2 + 2x - 3$.

You have $f(1) = 5(1)^2 + 2(1) - 3$

$= 5 + 2 - 3$

$= 4$

Also $f(1.18) = 5(1.18)^2 + 2(1.18) - 3$

$= 6.962 + 2.36 - 3$

$= 6.322$.

The average rate of change will be given by

$\frac{f(1.18) - f(1)}{1.18 - 1}$

$= \frac{6.322 - 4}{0.18}$

$= \frac{2.322}{0.18}$

$= 12.9$.

3. ok, thank you so much!

that really helped

(ps.anwser is 12.9 as 1.18-1 is .18 not 1)