Evaluate

e^{-5}
e
−5


using two approaches

e^{-x} = 1 – x + \frac{x^2}{2} - \frac{x^3}{3!} + …
e
−x
=1–x+
2
x
2



3!
x
3


+…

and

e^{-x} = \frac{1}{e^x} = \frac{1}{1+ x + \frac{x^2}{2} + \frac{x^3}{3!}+…}
e
−x
=
e
x

1

=
1+x+
2
x
2


+
3!
x
3


+…
1



and compare with the true value of

6.737947 \times 10^{-3}
6.737947×10
−3


. Use 20 terms to evaluate each series and compute true and approximate relative errors as terms are added