Linear graphs
A straight line is the friendliest graph in mathematics, and once you can read it, it tells you a whole story at a glance. In this lesson we plot points on the grid, build a line from a table of values, and meet the famous equation y = mx + c. We get to know its two parts — the gradient m (how steep, and whether it climbs, falls or stays flat) and the y-intercept c (where the line crosses the y-axis). Then we read equations straight off a graph, find a line through two points, draw a line from its equation, see why parallel lines share a gradient, and finish with real-life graphs like cost and distance–time.
By the end you should be able to (NSSCO Mathematics 7.2):
- Plot straight-line graphs from a table of values on a labelled grid
- Recognise and use the equation of a straight line in the form y = mx + c
- Understand the gradient m as rise ÷ run, and tell positive, negative and zero gradients apart
- Understand the y-intercept c as the point where the line crosses the y-axis
- Find the equation of a line from its graph, and from the coordinates of two points
- Draw a straight line when given its equation
- Know that parallel lines have equal gradients
- Interpret real-life linear graphs such as cost and distance–time, reading the intercept and gradient
Miss Jay Jay and Mike talk through the whole topic — with the figure and working drawn live.