Linear Functions in MYP Year 5 Maths
Master linear functions in MYP Year 5 Maths. Understand y=mx+c, calculate gradient and y-intercept, and graph straight lines confidently for MYP assessments.
The Equation of a Straight Line
Linear functions produce straight-line graphs and are written in the form y = mx + c, where m is the gradient and c is the y-intercept. At MYP Year 5, you are expected to work fluently with this form — graphing lines, identifying gradient and intercept from an equation, and constructing equations from graphs or given information.
Understanding Gradient
The gradient m describes how steep the line is and in which direction it goes. A positive gradient rises left to right; a negative gradient falls. Gradient is calculated as rise ÷ run, or using the formula:
m = (y₂ − y₁) / (x₂ − x₁)
Practise calculating gradient from two coordinate pairs, from a table of values, and from a graph. All three forms appear in MYP assessments.
The y-Intercept
The y-intercept is where the line crosses the y-axis — the value of y when x = 0. In y = mx + c, it is simply c. Make sure you can read it directly from an equation and from a graph.
Graphing Linear Functions
To graph y = mx + c: plot the y-intercept, then use the gradient to find a second point, then draw a straight line through both. Label the axes, mark key points, and always use a ruler. Criterion C marks can be lost for poorly presented graphs.
Common Mistakes
- Mixing up gradient and y-intercept when reading y = mx + c.
- Calculating gradient with the coordinates in the wrong order (x values where y values should go).
- Drawing a curve instead of a straight line — a linear function is always a straight line.
Building Confidence
Start by graphing lines given in y = mx + c form. Then practise rearranging equations into that form before graphing. Finally, practise writing the equation of a line from a graph or from two points — this is the level of skill expected in Criterion A and Criterion C tasks.