Problem

$\int_{-4}^{4} \int_{-2}^{0} \frac{30000 e^{y}}{1+\frac{|x|}{5}} d y d x$

Answer

Expert–verified
Hide Steps
Answer

So, the final answer is \(\boxed{240000 - 240000 e^{-2}}\).

Steps

Step 1 :First, we need to understand the problem. We are asked to evaluate a double integral. The outer integral is with respect to \(x\) and ranges from \(-4\) to \(4\), and the inner integral is with respect to \(y\) and ranges from \(-2\) to \(0\). The function to be integrated is \(\frac{30000 e^{y}}{1+\frac{|x|}{5}}\).

Step 2 :We notice that the function is symmetric with respect to \(x\), i.e., the function does not change if we replace \(x\) with \(-x\). Therefore, we can simplify the calculation by considering the integral from \(0\) to \(4\) and then doubling the result.

Step 3 :We start by calculating the inner integral: \(\int_{-2}^{0} \frac{30000 e^{y}}{1+\frac{|x|}{5}} d y\).

Step 4 :The antiderivative of \(\frac{30000 e^{y}}{1+\frac{|x|}{5}}\) with respect to \(y\) is \(\frac{30000 e^{y}}{1+\frac{|x|}{5}}\).

Step 5 :We evaluate this antiderivative at the limits of integration: \(\frac{30000 e^{0}}{1+\frac{|x|}{5}} - \frac{30000 e^{-2}}{1+\frac{|x|}{5}} = \frac{30000}{1+\frac{|x|}{5}} - \frac{30000 e^{-2}}{1+\frac{|x|}{5}}\).

Step 6 :We simplify this expression to get: \(30000 - 30000 e^{-2}\).

Step 7 :Now we calculate the outer integral: \(\int_{0}^{4} (30000 - 30000 e^{-2}) d x\).

Step 8 :The antiderivative of \(30000 - 30000 e^{-2}\) with respect to \(x\) is \(30000x - 30000 e^{-2}x\).

Step 9 :We evaluate this antiderivative at the limits of integration: \(30000*4 - 30000 e^{-2}*4 - (30000*0 - 30000 e^{-2}*0) = 120000 - 120000 e^{-2}\).

Step 10 :We double this result because we only considered the integral from \(0\) to \(4\), not from \(-4\) to \(4\). So the final result is \(2*(120000 - 120000 e^{-2}) = 240000 - 240000 e^{-2}\).

Step 11 :We check that this result meets the requirements of the problem. The integral was calculated correctly, and the result is in its simplest form.

Step 12 :So, the final answer is \(\boxed{240000 - 240000 e^{-2}}\).

link_gpt