Integral of an exponential over another exponential: .

Here substitution doesn't look fruitfulbecause of the different exponents. Perhaps we can handle the two terms of the numerator separately, using the Sum Rule for integrals:

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In the first term, we can use the Scalar Multiple Rule for integrals:

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Next we multiply both numerator and denominator by in both integrals:

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Next, we use the substitutions , and , :

Now we can use the Integral of an Exponential:

Finally, we substitute for u and v to get an expression in terms of x: