Writing Linear Graph Equation (y = mx +c)
Step-by-Step Method:
🎯 Goal: Write the equation of the line in the form
y= mx+c
Where:
m is the slope (also called the gradient),
c is the y-intercept (where the line crosses the y-axis).
Step 1: Find the Slope (m)
Use the slope formula if you're given two points on the graph:
If the points are A (x₁, y₁) and B (x₂, y₂):
Step 2: Find the Y-Intercept (c)
Now use the formula: y=mx+c
Substitute one of your points (x, y) and your value of m, and solve for c.
Step 3: Write the Equation
Now Substitute value of m and value of c into the equation: y=mx+c
Examples:
Example 1: A straight line L is shown on the grid. Findthe equation of line L.
Answer :
Example 2: The point A (1, 2) and the point B (4, 5) lie on the line K. Find the equation of the line K.
Answer :
Top Tips
✨ Always label your points clearly as (x₁, y₁) and (x₂, y₂). It helps avoid mix-ups!
✨ Watch the minus signs—especially if the y-values are negative!
✨ Choose the easier point when substituting to find c. It makes the maths simpler.
✨ Once you have the equation, try testing it with both points. Plug in the x and see if you get the correct y!