Is this true formula :$\lim_{x\to -\infty } \exp (x)=\exp(-\infty)=0$ for student in high school level?

Question

Inspectors of mathematics recomonded teachers that this formula $\exp(-\infty)$ as a second step for computation of $\lim_{x\to -\infty } \exp (x)$ as $x \to -\infty$ is not true in mathematics and it is a scientific error . In my Humbel opinion as a teacher in high school that the titled formula is true and there is no problem to consider it in any mathematical contexts , Now my question here is :

Is really this formula includes scientific error in mathematics $$\lim_{x\to -\infty } \exp (x)=\exp(-\infty)=0$$

?

Answer 1

$\exp(-\infty)$ has no sense, because $\exp$ is a function that takes as an argument a number, and $-\infty$ is not a number.

Answer 2

Formally $-\infty$ is not a real number, so $\exp(-\infty)$ does not make sense. However you may add the symbol $-\infty$ to the reals and define $\exp(-\infty)$ to be $\lim_{x \to -\infty} \exp x$.