# Thread: Using the difference quotient

1. ## Disregard/8-)figured Out Problem On My Own!! 8-)

using this formula, I'm trying to figure out the problem below

formula: f(a+h)-f(a)/h

Original prob is P(r)=500(1+r)^2
r=0.07 & h=0.01

I want to do this:

500(1+(r+h))^2/h

So 500(1+(0.07+0.01))^2 / 0.01

but it doesn't come ouut w/the answer in the book. Where am I going wrong? Can you help me step by step? Math is so hard for me to grasp. then they mix up the letters!

Thanks a bunch!

2. Originally Posted by crazydaizy78
using this formula, I'm trying to figure out the problem below

formula: f(a+h)-f(a)/h

Original prob is P(r)=500(1+r)^2
r=0.07 & h=0.01

I want to do this:

500(1+(r+h))^2/h

So 500(1+(0.07+0.01))^2 / 0.01

but it doesn't come ouut w/the answer in the book. Where am I going wrong? Can you help me step by step? Math is so hard for me to grasp. then they mix up the letters!

Thanks a bunch!
First off - good for you for being a donor

You need to break it down to small bits and then do each bit at a time:

1. P(r + h) = 500(1 + r + h)^2 = 500(1 + 0.07 + 0.01)^2 = 500(1.08)^2 = 583.2.

2. P(r) = 500(1 + r)^2 = 500(1 + 0.07)^2 = 500(1.07)^2 = 572.45.

3. $\displaystyle \displaystyle \frac{P(r + h) - P(r)}{h} = \frac{583.2 - 572.45}{0.01} = \frac{10.75}{0.01} = 1075$.