Table and graph of a function
Picture a Leaving Cert student on a Dublin Bus journey home with a Leap card, wondering how the fare changes with distance. Before you can analyse a function like that, you need to sketch it: choose the values of $x$ carefully, calculate their images and join the points sensibly, knowing which regions need more points than others. At the end we will come back to the Leap card fare.
Table of values: which points to choose
Given the linear function $f(x) = 2x - 3$: a) Complete a table of values for $x \in \{-2, 0, 1, 3\}$. b) Draw the graph of the function in the Cartesian plane using the…
Given the linear function $f(x) = 2x - 3$:
- a) Complete a table of values for $x \in \{-2, 0, 1, 3\}$.
- b) Draw the graph of the function in the Cartesian plane using the points obtained.
You can do it on paper and send a photo with your answer.
Consider the quadratic function $f(x) = x^2 - 4$: a) Calculate the images for $x = -3, -2, 0, 2, 3$ and organise the results in a table. b) Draw the graph of the…
Consider the quadratic function $f(x) = x^2 - 4$:
- a) Calculate the images for $x = -3, -2, 0, 2, 3$ and organise the results in a table.
- b) Draw the graph of the function and identify the coordinates of its vertex.
You can do it on paper and send a photo with your answer.
Calculate analytically the points of intersection with the x-axis and with the y-axis of the rational function $f(x) = \frac{3x+6}{x-1}$.
Calculate analytically the points of intersection with the x-axis and with the y-axis of the rational function $f(x) = \frac{3x+6}{x-1}$.
Identify whether the following table of values corresponds to a linear function or a quadratic function by calculating the differences between consecutive values of $y$.…
Identify whether the following table of values corresponds to a linear function or a quadratic function by calculating the differences between consecutive values of $y$. Then, find its algebraic expression $y = f(x)$.
| $x$ | $-1$ | $0$ | $1$ | $2$ | $3$ |
|---|---|---|---|---|---|
| $y$ | $1$ | $4$ | $7$ | $10$ | $13$ |
A quadratic function of the form $f(x) = ax^2 + bx + c$ passes through the points $(0, 3)$, $(1, 0)$ and $(2, -1)$. a) Set up and solve the system of equations to find…
A quadratic function of the form $f(x) = ax^2 + bx + c$ passes through the points $(0, 3)$, $(1, 0)$ and $(2, -1)$.
- a) Set up and solve the system of equations to find the values of $a, b$ and $c$.
- b) Using the algebraic expression obtained, calculate the vertex and construct a table of values to plot the parabola.
You can do it on paper and send a photo with your answer.
Rational and radical functions: points near the excluded value
In a rational function, the interesting values are near the value that makes the denominator zero, not far from it; in a radical function, the domain starts exactly where the radicand becomes zero.
It is desired to build a rectangular pen taking advantage of an existing wall for one of its sides. There are $20\text{ m}$ of wire fencing available for the other three…
It is desired to build a rectangular pen taking advantage of an existing wall for one of its sides. There are $20\text{ m}$ of wire fencing available for the other three sides.
- a) Express the area $A(x)$ of the pen as a function of the length $x$ of one of the sides perpendicular to the wall.
- b) Determine the valid domain of the function $A(x)$ in the context of the problem.
- c) Construct a table of values and use it to sketch the graph and find the dimensions that maximise the area.
You can do it on paper and send a photo with your answer.
Given the radical function $f(x) = \sqrt{x+2}$: a) Determine its domain analytically. b) Complete a table of values for $x \in \{-2, -1, 2, 7\}$ and use it to sketch the…
Given the radical function $f(x) = \sqrt{x+2}$:
- a) Determine its domain analytically.
- b) Complete a table of values for $x \in \{-2, -1, 2, 7\}$ and use it to sketch the graph.
Given the rational function $f(x) = \dfrac{3}{x - 4}$:\na) Before calculating any exact value, estimate what sign and what order of magnitude (very close to zero or very…
Given the rational function $f(x) = \dfrac{3}{x - 4}$:\na) Before calculating any exact value, estimate what sign and what order of magnitude (very close to zero or very large in absolute value) you expect $f(x)$ to take when evaluated at values very close to $4$, such as $x = 3.9$ and $x = 4.1$. Justify your prediction using the signs of the numerator and the denominator.\nb) Verify your estimation by calculating the values of the function for $x = 3.9$; $x = 3.99$; $x = 4.01$, and $x = 4.1$, and arrange them in a table of values.\nc) From the numerical results obtained, interpret what happens geometrically at the line $x = 4$ and reason whether it is a vertical asymptote.
The goal is to design the analytic formula of a rational function of the form $f(x) = \dfrac{ax + b}{x - c}$ so that it satisfies the following characteristics observed…
The goal is to design the analytic formula of a rational function of the form $f(x) = \dfrac{ax + b}{x - c}$ so that it satisfies the following characteristics observed in its key table of values:\n1. Its graph intersects the x-axis only at the point $(4, 0)$.\n2. Its graph intersects the y-axis at the point $(0, -2)$.\n3. The function is not defined at $x = 2$, having a vertical asymptote at that line.\na) Reasonably determine the values of the real constants $a$, $b$, and $c$.\nb) With the obtained function, create a strategic table of values that includes the intercepts with the axes and two values located immediately before and after the forbidden value ($x = 1.9$ and $x = 2.1$).\nc) Explain what happens to the values of $f(x)$ as the variable $x$ takes increasingly large positive values ($x = 100$, $x = 1000$) and deduce the equation of its horizontal asymptote.
To plot the graph of the function $f(x) = \dfrac{x^2 - 4x + 3}{x - 1}$, two students propose different methods:\n- Aoife's method: Directly build a table with seven…
To plot the graph of the function $f(x) = \dfrac{x^2 - 4x + 3}{x - 1}$, two students propose different methods:\n- Aoife's method: Directly build a table with seven consecutive integers: $x \in \{-1, 0, 1, 2, 3, 4, 5\}$, substituting directly into the given formula.\n- Darragh's method: Before calculating points, study the domain of the function, factor the numerator to see if it simplifies with the denominator for $x \ne 1$, and then create a strategic table with intercepts and values close to the discontinuities.\na) If Aoife's method is followed, what insurmountable problem arises exactly at $x = 1$? Could this lead to the erroneous conclusion that the line $x = 1$ is a vertical asymptote?\nb) Carry out Darragh's method: simplify the expression of $f(x)$ for all $x \ne 1$ and calculate the values of $f(x)$ for $x = 0.99$ and $x = 1.01$. Do these values grow without bound like at an asymptote, or do they approach a finite number?\nc) Compare both methods and justify which one is more reliable for avoiding false graphical interpretations. Precisely describe what geometric feature appears on the graph at the point with abscissa $x = 1$ (indicating its coordinates).
The mass $M(t)$ in grams of a radioactive isotope decreases over time $t$ (in days) according to the exponential function $M(t) = M_0 \times (0,5)^{\frac{t}{T}}$, where…
The mass $M(t)$ in grams of a radioactive isotope decreases over time $t$ (in days) according to the exponential function $M(t) = M_0 \times (0,5)^{\frac{t}{T}}$, where $M_0$ is the initial mass and $T$ is the half-life.
Given that at time $t=0$ there were $200\text{ g}$ of substance and after $60\text{ days}$ there are $50\text{ g}$ remaining:
- a) Calculate the values of the parameters $M_0$ and $T$.
- b) Construct a table of values for $t = 0, 30, 60, 90, 120$ and sketch the graph.
You can do it on paper and send a photo with your answer.
Given the rational function $f(x) = \frac{4}{x-2}$: a) Determine its domain. b) Construct a table of values evaluating the function at points close to $x = 2$ from the…
Given the rational function $f(x) = \frac{4}{x-2}$:
- a) Determine its domain.
- b) Construct a table of values evaluating the function at points close to $x = 2$ from the left and from the right ($x = 1.9; 1.99; 2.1; 2.01$).
- c) Based on the results obtained, what graphical feature does the function display at $x = 2$?
You can do it on paper and send a photo with your answer.
In a laboratory, the growth of a bacterial population is studied. The number of bacteria $N(t)$ in thousands is given by the function $N(t) = 100 \times 2^t$, where $t$…
In a laboratory, the growth of a bacterial population is studied. The number of bacteria $N(t)$ in thousands is given by the function $N(t) = 100 \times 2^t$, where $t$ is the time in hours.
- a) Construct a table of values for the first 4 hours ($t = 0, 1, 2, 3, 4$).
- b) Draw the graph of the function. What type of growth is observed?
You can do it on paper and send a photo with your answer.
Given the logarithmic function $f(x) = \log_2(x+4)$: a) Determine analytically its domain and the equation of its vertical asymptote. b) Construct a table of values by…
Given the logarithmic function $f(x) = \log_2(x+4)$:
- a) Determine analytically its domain and the equation of its vertical asymptote.
- b) Construct a table of values by choosing strategic values of $x$ that result in exact powers of base 2 for the argument of the logarithm.
- c) Plot the graph of the function.
You can do it on paper and send a photo with your answer.
Consider the function $f(x) = \sqrt{9-x^2}$. a) Calculate its domain of definition analytically. b) Make a table of values for $x \in \{-3, -2, 0, 2, 3\}$. c) Draw the…
Consider the function $f(x) = \sqrt{9-x^2}$.
- a) Calculate its domain of definition analytically.
- b) Make a table of values for $x \in \{-3, -2, 0, 2, 3\}$.
- c) Draw the graph of the function and state its range.
You can do it on paper and send a photo with your answer.
Piecewise functions: continuity at the junction
Given the modulus function $f(x) = |2x - 5|$: a) Evaluate the function at the points $x = 0; 2; 2.5; 3; 5$ and construct a table of values. b) Draw the graph of the…
Given the modulus function $f(x) = |2x - 5|$:
- a) Evaluate the function at the points $x = 0; 2; 2.5; 3; 5$ and construct a table of values.
- b) Draw the graph of the function.
You can do it on paper and send a photo with your answer.
Given the piecewise function: $f(x) = \begin{cases} -x + 2 & \text{if } x < 1 \\ 2x - 1 & \text{if } x \ge 1 \end{cases}$ a) Construct a table of values by evaluating…
Given the piecewise function:
$f(x) = \begin{cases} -x + 2 & \text{if } x < 1 \\ 2x - 1 & \text{if } x \ge 1 \end{cases}$
- a) Construct a table of values by evaluating the function at $x = -2; 0; 0.99; 1; 2; 3$.
- b) Draw the graph of the function and state whether it is continuous at $x = 1$.
You can do it on paper and send a photo with your answer.
Given the piecewise function depending on a parameter $k$: $f(x) = \begin{cases} x^2 - k & \text{if } x < 2 \\ 2x + 1 & \text{if } x \ge 2 \end{cases}$ a) Find the value…
Given the piecewise function depending on a parameter $k$:
$f(x) = \begin{cases} x^2 - k & \text{if } x < 2 \\ 2x + 1 & \text{if } x \ge 2 \end{cases}$
- a) Find the value of $k$ so that the two branches of the function "connect" at the point $x = 2$ (that is, so that the function is continuous).
- b) Using the value of $k$ found, construct a table of values in the interval $[0, 4]$ and sketch the graph of the function.
You can do it on paper and send a photo with your answer.
Given the absolute value function $f(x) = |x^2 - 4|$: a) Express the piecewise function by removing the absolute value. b) Find the axis intercepts. c) Construct a table…
Given the absolute value function $f(x) = |x^2 - 4|$:
- a) Express the piecewise function by removing the absolute value.
- b) Find the axis intercepts.
- c) Construct a table of values in the interval $[-3, 3]$ and draw its graph.
You can do it on paper and send a photo with your answer.
Reading a graph: trends and asymptotes
You do not always construct the graph: you also have to read it when it is already drawn, extracting information without needing the formula.
The following graph shows the evolution of the temperature $T$ (in $^\circ\text{C}$) of a cup of coffee as a function of time $t$ (in minutes) since it is served. From…
The following graph shows the evolution of the temperature $T$ (in $^\circ\text{C}$) of a cup of coffee as a function of time $t$ (in minutes) since it is served.
From the graph:
- a) State the initial temperature of the coffee.
- b) What value does the temperature approach as a large amount of time elapses? What physical meaning does the horizontal asymptote have?
- c) Is the function increasing or decreasing? Justify your answer.
Observe the following graph of a function $f(x)$ defined by straight-line segments: From the graph, determine: a) The domain and range of the function. b) The value of…
Observe the following graph of a function $f(x)$ defined by straight-line segments:
From the graph, determine:
- a) The domain and range of the function.
- b) The value of $f(-2)$ and $f(1)$.
Observe the following graph of a rational function of the form $f(x) = \frac{ax+b}{cx+d}$: From the information provided by the graph (asymptotes and axis intercepts):…
Observe the following graph of a rational function of the form $f(x) = \frac{ax+b}{cx+d}$:
From the information provided by the graph (asymptotes and axis intercepts):
- a) Determine the domain and range of the function.
- b) Deduce the algebraic expression of the function $f(x)$.
The following figure shows the graph of the exponential function $f(x) = 2^x$ and the line $y = x$. a) From the highlighted points on the blue curve of $f(x)$, construct…
The following figure shows the graph of the exponential function $f(x) = 2^x$ and the line $y = x$.
- a) From the highlighted points on the blue curve of $f(x)$, construct a table of values for its inverse function $f^{-1}(x)$.
- b) Draw the graph of the inverse function in your exercise book using symmetry with respect to the line $y=x$.
- c) Write the algebraic expression for $f^{-1}(x)$.
You can do it on paper and send a photo with your answer.