Subtracting Integers

Subtracting integers by adding the opposite

\begin{align} 5 - 9 & &&\textit{Given} \\\ 5 - 9 &= 5 + {\color{red}(-9)} &&\textit{Add the opposite} \\\ &= - 4 &&\textit{Solution} \\\ \end{align}

Guided Practice

Use a number line to find each difference. Note: “Difference” is the answer to a subtraction problem.

\begin{align} 4-7 &= \tag 1 \\\ -6-5 &= \tag 2 \\\ 2-(-4) &= \tag 3 \\\ -8-(-2) &= \tag 4 \end{align}

Find each difference. Use a number line only if you need to, or to check.

\begin{align} 6-10 &= \tag 5 \\\ -3-(-8) &= \tag 6 \\\ -1-9 &= \tag 7 \\\ -12-(-2) &= \tag 8 \end{align}

Evaluate $ a-b $ for each set of values.

\begin{align} a-b \text{; when } a=9 \textit{, } b=-7 \tag 9 \\\ a-b \text{; when } a=-8 \textit{, } b=6 \tag{10} \\\ a-b \text{; when } a=4 \textit{, } b=18 \tag{11} \\\ \end{align}

Real-World Challenge

In 1980, in Great Falls, Montana, the temperature rose from $-32^o F$ to $15^o F$ in seven minutes. How much did the temperature increase?

$$ |-35| + |15| = 50^o F $$