Example 1.1.5 Add Two Negative Numbers

If you needed to add \(-18\) and \(-7\text{,}\) note that both are negative. Maybe you have this expression in front of you:

\begin{equation*} -18+-7 \end{equation*}

but that “plus minus” is awkward, and in this book you are more likely to have this expression:

\begin{equation*} -18+(-7) \end{equation*}

with extra parentheses. (How many subtraction signs do you see? How many negative signs?)

Since both our terms are negative, we can add \(18\) and \(7\) to get \(25\) and immediately realize that our final result should be negative. So our result is \(-25\text{:}\)

\begin{equation*} -18+(-7)=-25 \end{equation*}