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Pb 6 exam 2019

Hi,
Could you explainwhy do we choose f2 for x positive and f1 otherwise?
I donkt get the thing about the absolute values,
Thank you so so much!Screenshot_2022-01-12-10-32-07-163.jpeg

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If x >0 and is huge then \(e^x\) will be a very big number and we're given in the question that we can't deal with numbers that have a large absolute value. Hence \(f_{1}\) will run into exactly this problem and consequently it's not suitable. The same argument goes for x having a large negative value and \(e^{-x} \)

My understanding is that if x is > 0 and x is very large (x--> inf) then exp(-x) --> 0, but exp(x) --> inf. So computing f2(x) does not cause problems, while computing f1(x) might cause problems.
If x < 0 and x is very large (w --> -inf), then exp(-x) --> inf, but exp(x) --> 0. So computing f1(x) does not cause problems, while computing f2(x) might cause problems.

Top comment

If x >0 and is huge then \(e^x\) will be a very big number and we're given in the question that we can't deal with numbers that have a large absolute value. Hence \(f_{1}\) will run into exactly this problem and consequently it's not suitable. The same argument goes for x having a large negative value and \(e^{-x} \)

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