Tables of values, plotting points accurately and joining them the right way, and reading answers back off your own graph.
What you will learn
- Complete a table of values for a linear, quadratic, cubic, reciprocal or exponential equation
- Plot points to within half a small square
- Join points with a ruler or a smooth curve, as the graph needs
- Use your graph to solve an equation or read a value
From equation to table
A graph question nearly always starts with a table of values.
Work out y for each x, one column at a time.
- write the equation with y on its own: 2y = 3x − 2 becomes y = (3x − 2) ÷ 2
- put each x in brackets when it is negative: x = −2 gives y = (3 × (−2) − 2) ÷ 2 = −4
- for x², square first: (−3)² = 9, never −9
- check the pattern: a straight line goes up or down by the same amount each step
The usual slip: (−3)² typed into a calculator as −3² gives −9. Use the brackets.
The rest of this lesson and its 12 practice questions are locked.
In this lesson
- From equation to table
- Plotting and joining
- Reading answers from your graph
- Choosing a line to draw (Higher)
- Try it: An easy one first
12 practice questions, marked as you go; about 25 minutes in all.
Key terms
Ruler, Smooth curve
In this unit: Drawing and constructing
The answers papers ask you to draw: graphs plotted from a table, sketches with their key points, statistical charts, ruler-and-compass constructions and loci, each checked the way a mark scheme checks it.