Piecewise-defined functions
A car park charges one price for the first hour and a different one for each extra hour. A mobile data plan changes its price after a certain amount of usage. These situations cannot be written with a single formula valid for every $x$: they need several formulas, each with its own interval. They are called piecewise-defined functions.
What a piecewise function is
Each piece only "exists" within its own interval: outside it, that expression is not used. That is why every formula in the brace always needs its condition.
Determine the domain and range of the piecewise function whose algebraic expression is:…
Determine the domain and range of the piecewise function whose algebraic expression is:
$f(x) = \begin{cases} -1 & \text{if } -3 \le x < 0 \\ 1 & \text{if } 0 \le x \le 3 \end{cases}$
Calculating values: choose the piece first
To calculate $f(a)$, the first step is always to look at which piece $a$ falls in, and only then substitute into the corresponding formula.
Given the following piecewise function: $f(x) = \begin{cases} 2x + 5 & \text{if } x < -1 \\ 3 & \text{if } -1 \le x \le 2 \\ -x + 4 & \text{if } x > 2 \end{cases}$…
Given the following piecewise function:
$f(x) = \begin{cases} 2x + 5 & \text{if } x < -1 \\ 3 & \text{if } -1 \le x \le 2 \\ -x + 4 & \text{if } x > 2 \end{cases}$
Calculate the value of the function at the points $x = -3$, $x = -1$, $x = 0$, $x = 2$ and $x = 5$.
Find the axis intercepts of the piecewise function: $f(x) = \begin{cases} x + 3 & \text{if } x < 0 \\ 2x - 4 & \text{if } x \ge 0 \end{cases}$
Find the axis intercepts of the piecewise function:
$f(x) = \begin{cases} x + 3 & \text{if } x < 0 \\ 2x - 4 & \text{if } x \ge 0 \end{cases}$
Graphing and studying continuity
To graph a piecewise function, draw each piece only within its interval, marking with a filled dot the endpoint that belongs to the piece (the one with $\leq$ or $\geq$) and with an open dot the one that does not.
Draw the graph of the following piecewise function in your exercise book: $f(x) = \begin{cases} x + 2 & \text{if } x \le 1 \\ 3 & \text{if } x > 1 \end{cases}$ State…
Draw the graph of the following piecewise function in your exercise book:
$f(x) = \begin{cases} x + 2 & \text{if } x \le 1 \\ 3 & \text{if } x > 1 \end{cases}$
State whether the function is continuous at $x = 1$.
You can do it on paper and send a photo with your answer.
Draw the graph of the function defined by: $f(x) = \begin{cases} -2 & \text{if } x < -2 \\ x & \text{if } -2 \le x \le 2 \\ 2 & \text{if } x > 2 \end{cases}$ You can do…
Draw the graph of the function defined by:
$f(x) = \begin{cases} -2 & \text{if } x < -2 \\ x & \text{if } -2 \le x \le 2 \\ 2 & \text{if } x > 2 \end{cases}$
You can do it on paper and send a photo with your answer.
Draw the graph of the following function and classify its points of discontinuity, if any:…
Draw the graph of the following function and classify its points of discontinuity, if any:
$f(x) = \begin{cases} -2x - 4 & \text{if } x < -1 \\ 2 & \text{if } -1 \le x < 2 \\ x - 1 & \text{if } x \ge 2 \end{cases}$
You can do it on paper and send a photo with your answer.
The absolute value as a piecewise function
Express the modulus function $f(x) = |x - 4|$ as a piecewise function, removing the modulus bars.
Express the modulus function $f(x) = |x - 4|$ as a piecewise function, removing the modulus bars.
Express the function $f(x) = |2x + 6| - 3$ as a piecewise function and draw its graph. Find the coordinates of its vertex (the point where the slope changes).
Express the function $f(x) = |2x + 6| - 3$ as a piecewise function and draw its graph. Find the coordinates of its vertex (the point where the slope changes).
Tiered tariffs
Piecewise functions are the natural model for any tariff whose price changes after a certain amount of usage or time.
A public car park charges the following rates: $2$ euros for the first hour (or part thereof) and $1$ euro for each additional hour thereafter. Write the algebraic…
A public car park charges the following rates: $2$ euros for the first hour (or part thereof) and $1$ euro for each additional hour thereafter. Write the algebraic expression of the function $C(t)$ determining the cost in euros in terms of the time $t$ in hours, up to a maximum parking time of $3$ hours.
The temperature $T$ (in $^\circ\text{C}$) of an industrial ceramics kiln varies depending on the time $t$ (in hours) since it is switched on. During the first $2$ hours,…
The temperature $T$ (in $^\circ\text{C}$) of an industrial ceramics kiln varies depending on the time $t$ (in hours) since it is switched on. During the first $2$ hours, the temperature rises from $20^\circ\text{C}$ at a constant rate of $400^\circ\text{C}$ per hour. Then, it remains constant for $3$ hours. Finally, it is turned off and the temperature decreases at a constant rate of $200^\circ\text{C}$ per hour until returning to $20^\circ\text{C}$.
Write the algebraic expression of the piecewise function $T(t)$.
The graph summarises the behaviour of the kiln:
Calculate the value of the parameters $a$ and $b$ so that the following function is continuous on the set of all real numbers $\mathbb{R}$:…
Calculate the value of the parameters $a$ and $b$ so that the following function is continuous on the set of all real numbers $\mathbb{R}$:
$f(x) = \begin{cases} ax + b & \text{if } x < -1 \\ x^2 - 2x & \text{if } -1 \le x < 2 \\ \frac{a}{x} + b & \text{if } x \ge 2 \end{cases}$
Back to the start: If a car park charges 2 € for the first hour and 1{,}50 € for each extra hour, the total price depending on the time $t$ (in hours) is the piecewise function $P(t) = 2$ if $0 < t \le 1$, and $P(t) = 2 + 1{,}50(t - 1)$ if $t > 1$.