4.2 Function Notation
Notes
$f(x)$ is read "$f$ of $x$" and means the output of function $f$ for input $x$. It does not mean $f$ times $x$.
- Evaluate: if $f(x) = 3x - 2$, then $f(4) = 3(4) - 2 = 10$.
- Solve for an input: if $f(x) = 13$, then $3x - 2 = 13$, so $x = 5$.
- On a graph, $f(a) = b$ means the point $(a, b)$ is on the graph.
Practice
If $g(x) = x^2 - 4x$, what is $g(-1)$?
$(-1)^2 - 4(-1) = 1 + 4 = 5$.
If $h(x) = 2x + 7$ and $h(a) = 1$, then $a =$
$2a + 7 = 1 \Rightarrow 2a = -6$.
The point $(3, -2)$ is on the graph of $f$. Which statement is true?
Input 3 gives output $-2$.
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