In this case, and represents the basis of natural or neperian logarithms. It's the irrational number and whose approximate value is 2,7182818.
See the table with values of x it's from .
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We note that as .
Similarly, making the replacement we have:
Even more generally, we have:
The above two forms give the immediate solution to exercises of this type and avoid algebraic substitutions.
If ,So .
How x 0 then u 0. Therefore:
Generalizing the above property, we have .