In the Real World Examples

The perimeter P of a rectangle with length l and width w is given by P = l + l + w + w. How can this formula be better expressed?

If we used this version of the formula, we'd need to add l + l and w + w every time we performed a substitution. It's way more efficient to use the formula P = 2l + 2w. This way we've already added l + l and w + w. It occupies less space and kills fewer trees, and we're less likely to need to deal with something like what Mark Wahlberg went through in The Happening. Did you see that movie? That was terrifying. Chills.