# Math Help - Using Calculator for Integration

1. ## Using Calculator for Integration

Suppose that a company's marginal revenue from the manufacture and sales of eggbeaters is dr/dt = 2- 2/(x+1)^2 where r is measured in thousands of dollars and x in thousands of units. How much money should a company expect from a production run of 3 thousand eggbeaters?

I tried integrating it on my calculator and got 5998.000666

2. Shouldn't it be $\frac{dr}{dx} = 2 - \frac{2}{(x + 1)^2}$? If so, wouldn't you calculate the definite integral $\int_0^3 [2 - \frac{2}{(x + 1)^2}] \, dx$?

My calculator returns $\frac{9}{2} = 4.5$ so if my reasoning is correct then the answer is $4,500. 3. Originally Posted by NOX Andrew Shouldn't it be $\frac{dr}{dx} = 2 - \frac{2}{(x + 1)^2}$? If so, wouldn't you calculate the definite integral $\int_0^3 [2 - \frac{2}{(x + 1)^2}] \, dx$? My calculator returns $\frac{9}{2} = 4.5$ so if my reasoning is correct then the answer is$4,500.
Ok I agree with that integration. Your just saying that it should dr/dx = instead of dr/dt = ?

4. Yes; I believe the integral would be invalid if it were $\frac{dr}{dt}$.