# Math Help - How can I solve these problems using TI-89

1. ## How can I solve these problems using TI-89

Given the revenue of the function

r=250q+45q^2-q^3

Using differentials, find the approximate change in profit if the level of production changes from q=90 to q=91. Find the true change.

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I'm really stuck, can someone help me out? Do I need to use the integration tool to solve this?

2. ## Re: How can I solve these problems using TI-89

Originally Posted by own3dripy
Given the revenue of the function

r=250q+45q^2-q^3

Using differentials, find the approximate change in profit if the level of production changes from q=90 to q=91. Find the true change.

----

I'm really stuck, can someone help me out? Do I need to use the integration tool to solve this?
First of all, you can only ever calculate profit if you subtract the costs from the revenue. Do you have the costs?