# integral of sqrt(x)*e^(-x) from 0 to inf | Summary and Q&A

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May 4, 2017
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integral of sqrt(x)*e^(-x) from 0 to inf

## TL;DR

The content discusses the process of integrating the function s(x) * e^(-x) from 0 to infinity using a substitution method.

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### Q: Why is the usual approach for finding U not applicable in this case?

The exponent of e is -x, which is more complicated than s(x). Therefore, letting U be equal to s(x) will not work in this scenario.

### Q: How does substituting U = square root of x help simplify the integral?

By substituting U, the integral can be transformed into a new integral in terms of U, making it easier to work with.

### Q: How is integration by parts utilized in solving the integral?

Integration by parts is used to break down the integral into two parts, one of which is integrable. The product of these parts is used to find the answer to the original integral.

### Q: What is the significance of the result being equal to half of the famous Gaussian integral?

The result being equal to half of the Gaussian integral demonstrates a mathematical relationship and highlights the connection between different areas of mathematics.

## Summary & Key Takeaways

• The video explains the difficulties in integrating the given function and introduces the substitution method as a possible approach.

• The substitution is made by setting u = square root of x and differentiating both sides to find the value of dx.

• The integral is then transformed into a new integral in terms of u, and the method of integration by parts is applied.