Straight-line graphs
Pages
Horizontal and vertical lines
Why x = 3 is a vertical line and y = 3 a horizontal one.
Plotting a line from a table of values
Filling a table, plotting the points, and using a stray point as a check.
The gradient of a line
Measuring steepness as rise over run, the sign showing climb or fall.
The equation y = mx + c
Reading the gradient and y-intercept straight from the equation.
Reading an equation off a graph
Finding the intercept on the y-axis and the gradient from a whole-square.
Lines not written as y = mx + c
Rearranging equations like 2x + 3y = 6 before reading the gradient off.
The line through a point with a given gradient
Substituting the point into y = mx + c to find c, then writing the equation out.
The line through two points
Finding the gradient from the two points, then the intercept from either.
Parallel lines
Lines with equal gradients never meet, and writing a parallel line’s equation.
Perpendicular lines
Gradients of perpendicular lines multiply to −1.
Practice
The gradient of a line
Measuring steepness as rise over run, the sign showing climb or fall.
PracticeThe equation y = mx + c
Reading the gradient and y-intercept straight from the equation.
PracticeReading an equation off a graph
Finding the intercept on the y-axis and the gradient from a whole-square.
PracticeLines not written as y = mx + c
Rearranging equations like 2x + 3y = 6 before reading the gradient off.
PracticeThe line through a point with a given gradient
Substituting the point into y = mx + c to find c, then writing the equation out.
PracticeThe line through two points
Finding the gradient from the two points, then the intercept from either.
PracticeParallel lines
Lines with equal gradients never meet, and writing a parallel line’s equation.
PracticeStraight-line graphs review
Gradient, intercept, parallel and perpendicular.