Domain and Range

Find the domain and range of f = {($1$, $3$), ($2$, $5$), ($3$, $7$), ($4$, $9$)}.

• 1The domain is every input value: $1$, $2$, $3$, $4$.
• 2The range is every output value: $3$, $5$, $7$, $9$.

Answer: Domain = {$1$, $2$, $3$, $4$}, Range = {$3$, $5$, $7$, $9$}

f($x$) = $x^2$ is defined only for the inputs {$-2$, $-1$, $0$, $1$, $2$}. Find the range.

• 1Work out f($x$) for every input in the domain:
• 2f$(-2)=4$, f$(-1)=1$, f($0$) = $0$, f($1$) = $1$, f($2$) = $4$
• 3Collect the distinct outputs: $4$, $1$, $0$ (do not repeat $4$ and $1$)

Answer: Range = {$0$, $1$, $4$}