Non-linear graphs and real-life graphs

边玩边学

回答这些题目来赚取能量，然后钓鱼探索。无需账号。

给教育者：面向 Non-linear graphs and real-life graphs（KS3 Maths，Algebra）的即用型课程幻灯片, 复习笔记——用在你的课堂上，或将该知识点作为学习者可实时游玩的互动课堂活动来运行。

课程笔记

Plotting Quadratic Graphs

A quadratic graph has equation y = ax² + bx + c, where a, b and c are numbers and a ≠ 0.
To plot one, make a table of values: choose x-values, work out y for each, then plot the (x, y) points.
The points join to form a smooth curve called a parabola — never join them with straight lines.
If a is positive the parabola opens upwards (a U shape); if a is negative it opens downwards (an n shape).
The graph is symmetric about a vertical line through its turning point (the vertex).
Example: for y = x², values are (−2, 4), (−1, 1), (0, 0), (1, 1), (2, 4).

Roots from a Graph

The roots of an equation are the x-values where the graph crosses the x-axis (where y = 0).
Read them off by finding the x-coordinates of the crossing points.
A quadratic can cross the x-axis twice (two roots), touch it once (one repeated root), or miss it (no real roots).
Example: y = x² − 4 crosses at x = −2 and x = 2, so its roots are −2 and 2.

Cubic and Reciprocal Graphs

A cubic graph has an x³ term, e.g. y = x³; it has a characteristic S-shaped curve.
A cubic can cross the x-axis up to three times, so it can have up to three roots.
A reciprocal graph has equation y = k/x (k a number, x ≠ 0).
Reciprocal graphs have two separate branches and never touch either axis.
As x gets large, y = k/x gets close to 0, so the x-axis is an asymptote.

Distance–Time Graphs

On a distance–time graph, time is on the horizontal axis and distance from the start is on the vertical axis.
The gradient (steepness) of the line gives the speed.
A horizontal line means the object is stationary (not moving).
A steeper line means a faster speed; a straight line means constant speed.
Speed = distance ÷ time, so gradient = change in distance ÷ change in time.

Conversion Graphs

A conversion graph changes one unit into another, e.g. pounds to dollars or kilometres to miles.
It is usually a straight line through the origin, because the conversion rate is constant.
To convert a value, start on one axis, go up/across to the line, then across/down to the other axis.
The gradient equals the conversion rate (how much of one unit equals one of the other).

Real-Life Graphs: Filling Containers

A graph of depth against time shows how quickly a container fills.
A straight sloping line means the container fills at a steady rate (a uniform shape, like a cylinder).
A curve getting steeper means the container is widening as it fills.
A curve getting shallower means the container is narrowing as it fills.
A horizontal section means filling has paused.

Real-Life Graphs: Phone Tariffs

A phone tariff graph often plots cost against usage (minutes or data).
A fixed monthly fee appears as a starting value on the cost axis (the y-intercept).
A charge per unit appears as the gradient of the line.
A flat rate after an allowance shows as a horizontal line once the included amount is used up.
Comparing two tariffs means seeing where their lines cross — the point where costs are equal.

Reading and Interpreting Any Graph

Always check the axes: what each one measures and the scale used.
The gradient tells you the rate of change (how fast y changes as x increases).
A positive gradient means y increases as x increases; a negative gradient means y decreases.
Where a graph crosses the x-axis gives the roots; where it crosses the y-axis gives the intercept.
Use the shape of the curve to describe the real situation it represents.

幻灯片

Step through every slide for this topic — plus flashcards and revision notes — with a free account.

练习题

免费预览——62 题中的 8 题。注册即可查看全部。

1.The graph of a function is the set of ordered pairs (x, y). Which equation shows the relationship between x and y in these pairs?
Easy
- Ax = f(y)
- By = f(x)
- Cy = x
- Df(x) = x
2.The graph of y = x² is a straight line.
Easy
True or false?
3.A table of values for y = x² + 2x + 1 is shown. What is the value of y when x = 2? | x | -2 | -1 | 0 | 1 | 2 | | y | 1 | 0 | 1 | 4 | ? |
Easy
- A5
- B7
- C9
- D11
4.Which of these graphs are non-linear? (select all that apply)
Medium
- Ay = x²
- By = 3x - 1
- Cy = x³
- Dy = 2/x
- Ey = 5
5.Match each equation to the shape of its graph.
Medium
- y = x²
- y = x³
- y = 1/x
- y = x
- Parabola (U-shaped curve)
- Curve with an S-shape through the origin
- Two curved branches with asymptotes
- Straight line through the origin
6.On a distance-time graph, a horizontal line means the object is:
Medium
- Amoving at constant speed
- Baccelerating
- Cstationary
- Dmoving backwards
7.Put these steps in order to plot the graph of y = x² - 3x + 2.
Medium
- Draw the axes with a suitable scale
- Complete a table of values for chosen x-values
- Plot the coordinate pairs
- Join the points with a smooth curve
8.A conversion graph for pounds (£) and euros (€) passes through (0, 0) and (10, 12). How many euros is £25?
Medium
- A24
- B27
- C30
- D32

复习笔记

## Non-linear graphs and real-life graphs **The graph of a function** is the set of ordered pairs (x, y) where f(x) = y. Plotted on Cartesian axes, these points usually form a curve. ### Quadratic graphs - Form: y = x^2 + bx + c - Plot from a table of values: choose x values, work out y, plot the points, join with a smooth curve. - Shape: a **parabola** — a symmetrical U-shape (or n-shape if the x^2 coefficient is negative). - **Roots**: where the curve crosses the x-axis (y = 0). Read them off the graph. ### Cubic and reciprocal graphs - **Cubic**: highest power x^3, e.g. y = x^3. An S-shaped curve. - **Reciprocal**: y = 1/x (a fraction with x on the bottom). Two separate branches that get close to the axes but never touch them. ### Real-life graphs - **Distance–time graph**: distance on the vertical axis, time on the horizontal. The **gradient** gives the speed. A horizontal line means stationary; a steeper line means faster. - **Conversion graphs**: straight lines used to change between units (e.g. pounds and kilograms). Read across and down to convert. - **Filling containers**: the shape of the graph shows how quickly the depth rises — wide containers fill slowly (shallow gradient), narrow parts fill quickly (steep gradient). - **Phone tariffs**: compare fixed charges plus a rate per unit by comparing the lines. ### Exam tips - Always label axes and use a sensible scale. - Join plotted points with a smooth curve for quadratics and cubics — never dot-to-dot straight lines. - For real-life graphs, check what each axis represents before reading values. - Gradient = change in y / change in x.

Graph of a function: The set of ordered pairs (x, y) where f(x) = y; plotted on axes it usually forms a curve.
Parabola: The symmetrical U-shaped curve produced by a quadratic graph such as y = x^2 + bx + c.
Roots: The x-values where a graph crosses the x-axis, i.e. where y = 0.
Cubic graph: A graph whose highest power of x is 3, e.g. y = x^3; it has an S-shaped curve.
Reciprocal graph: A graph of the form y = 1/x, with two separate branches that approach but never touch the axes.
Distance–time graph: A graph with distance on the vertical axis and time on the horizontal axis; its gradient gives the speed.
Conversion graph: A straight-line graph used to change between two units, read by going across and down.
Gradient: The steepness of a line, found by change in y divided by change in x.

闪卡

What is the graph of a function f?

The set of ordered pairs (x, y) where f(x) = y. Plotted on axes, these points usually form a curve.

What shape is the graph of a quadratic function y = x² + bx + c?

A parabola — a smooth U-shaped (or upside-down U-shaped) curve.

How do you plot a quadratic graph such as y = x² + bx + c?

Make a table of values: choose x-values, work out each y-value, plot the points, then join them with a smooth curve.

What is a root of a graph?

An x-value where the graph crosses the x-axis, i.e. where y = 0.

How do you read the roots of a quadratic from its graph?

Find where the curve crosses the x-axis and read off the x-coordinates of those points.

What is the general shape of a cubic graph such as y = x³?

An S-shaped curve that can rise or fall steeply; it may cross the x-axis up to three times.

What is the general shape of a reciprocal graph such as y = 1/x?

Two separate curved branches that get closer to the axes but never touch them (asymptotes).

On a distance–time graph, what does the gradient represent?

Speed. A steeper line means a faster speed; a horizontal line means stationary (zero speed).

On a distance–time graph, what does a horizontal line mean?

The object is stationary — distance is not changing as time passes.

What is a conversion graph used for?

To convert between two units (e.g. miles and kilometres, or pounds and kilograms) by reading values from a straight-line graph.

How do you use a conversion graph to change 5 miles into kilometres?

Find 5 on the miles axis, go up to the line, then across to the kilometres axis and read the value.

What does a real-life graph of filling a container show?

How the depth (or volume) of water changes over time. The shape of the graph depends on the container's width at each height.

For a container that gets wider as it fills, what does the depth–time graph look like?

The graph gets less steep over time, because each extra unit of depth needs more water to raise the level.

What does a phone tariff graph usually compare?

The total monthly cost against the number of minutes (or texts/data) used, often as straight lines with different fixed charges and rates.

On a phone tariff graph, what does the y-intercept represent?

The fixed monthly charge — the cost when no minutes are used.

On a phone tariff graph, what does the gradient represent?

The cost per minute (or per unit) charged for usage.

How can you tell which of two phone tariffs is cheaper for a given number of minutes?

At that number of minutes, read the cost from each line; the lower line gives the cheaper tariff.

What is the difference between a linear and a non-linear graph?

A linear graph is a straight line (constant gradient); a non-linear graph is curved (gradient changes).

What does the gradient of a straight-line graph tell you?

The rate of change of y with respect to x — how much y increases for each unit increase in x.

How do you find the gradient of a straight line from a graph?

Choose two points on the line, then gradient = (change in y) ÷ (change in x).

What does the y-intercept of a graph represent in a real-life context?

The starting value of the quantity when the input (often time) is zero.

Why are graphs useful in real life?

They show how one quantity changes with another, making patterns, rates and comparisons easy to see.

Unlock all 62 questions, flashcards & more

创建免费账号，即可查看该知识点的每一道题、幻灯片、闪卡和复习笔记。

历年真题

该知识点的历年真题练习即将推出。

即将推出