# Homework Help: Rate of change ball thrown

Tags:
1. Feb 16, 2015

### Niaboc67

1. The problem statement, all variables and given/known data

3. The attempt at a solution
As far as I know those are correct. Could I have some assistance on how to solve for the rate of change? I know the formula is f(b)-f(a)/b-a but not sure how to go about it

2. Feb 16, 2015

### SteamKing

Staff Emeritus
What if f(t) = h(t)? Could you pick two times, t1 = a and t2 = b, and calculate the rate of change, knowing h(t) as a function of t?

3. Feb 17, 2015

### Brian T

That formula is saying take the change in height f(b) - f(a) and divide by the change in time b - a. Essentially, avg rate = total displavement over time for that displacement

4. Feb 17, 2015

### HallsofIvy

Unfortunately most of the answers you give here are wrong. You are given that $h(t)= 56t- 16t^2= -16(t^2- (7/2)t)$. Completing the square gives $h(t)= -16(t- 7/2)^2+ 196$.

5. Feb 17, 2015

### Staff: Mentor

@HallsofIvy: You got a factor of 2 wrong for the last equation.

6. Feb 21, 2015

### Staff: Mentor

Use parentheses!
What you wrote is the same as $f(b) - \frac{f(a)}{b} - a$.

If you write a fraction such as the one above in single-line text, it has to be written as (f(b) - f(a))/(b - a).