Aside from the = sign, you can start a formula by using a + sign. While you can say that this is "useless", the main function of this is to just multiply the whole formula with +1, that's why it appears as if nothing happened.
For the - sign, the inverse is true. It multiples the whole formula by -1, meaning a positive output of a formula becomes negative, and a negative output of a formula becomes positive. This can be useful in a number of applications.
For more tips on excel and financial models
, you can check this out. Hope this helps!