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**The limit of case 2**

We have two rather algebraically differently looking solutions, an exponential but as *r*_{1} → *r*_{2} the limit of the second case ought to be the first case. Before you read any further, why not try to figure it out yourself?

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Ok, back again. Let us have a look at

Now let us do the substitution

That means that

and thus that

But we know that

and thus that

I.e. the solution we found in case 1.

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