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Auralith Learning

Year 8 · Maths · Coordinates and straight lines · Lesson 2

Plotting straight-line graphs

Learn to make a table of values, plot and draw straight-line graphs like y = 2x + 1, read values from a graph, and check whether a point lies on a line.

Whiteboard video lesson: Plotting straight-line graphs

33-minute video lesson

Teaching, worked examples and 20 practice questions solved step by step.

Watch free for a month

What your child will learn

  • Substitute values into an equation like y = 2x + 1
  • Complete a table of values
  • Plot and draw a straight-line graph
  • Read values from a graph
  • Check whether a point lies on a line

The method

  1. Make a table of values.
  2. Put each x value into the equation to find y.
  3. Plot each (x, y) point.
  4. Join the points with a ruler, edge to edge.

Key words: table of values, substitute, plot, straight line, y-axis.

Worked examples

The first three practice questions from the lesson, with every step.

Question 1

Complete the table of values for y = 2x + 3.

  1. Step 1: Look at the table
  2. Step 2: x = 0: 2 × 0 + 3 = 3
  3. Step 3: x = 1: 2 × 1 + 3 = 5
  4. Step 4: x = 2: 2 × 2 + 3 = 7
  5. Step 5: x = 3: 2 × 3 + 3 = 9

Answer: y: 3, 5, 7, 9

Question 2

Complete the table of values for y = x − 4.

  1. Step 1: Look at the table
  2. Step 2: x = −1: (−1) − 4 = −5
  3. Step 3: x = 0: 0 − 4 = −4
  4. Step 4: x = 1: 1 − 4 = −3
  5. Step 5: x = 2: 2 − 4 = −2

Answer: y: −5, −4, −3, −2

Question 3

Complete the table of values for y = 4x.

  1. Step 1: Look at the table
  2. Step 2: x = −2: 4 × (−2) = −8
  3. Step 3: x = −1: 4 × (−1) = −4
  4. Step 4: x = 0: 4 × 0 = 0
  5. Step 5: x = 1: 4 × 1 = 4

Answer: y: −8, −4, 0, 4