The Equation for a Straight Line, y = mx + c

The formula ​y​ = ​mx​ + ​c​ represents a linear equation that plots a straight line on a graph. The y and x represent the axes, m the gradient and c the y-intercept (where the line crosses the y-axis).

Let’s look at a manipulation to find the equation for a straight-line using the following equation:

Rearrange for y

Subtract 12x from both sides…

Divide all terms by the coefficient of y

This reduces ​y​ to 1

The equation gives a straight-line graph with a gradient of -2 and a y-intercept equal to 5.

Graph of y = -2x + 5

Check

Set ​x​ = 0 in your equation (this will give the y-intercept value, c, if your calculation is correct).

When x = 0, y = 5 (Setting y = 0 would give you the x-intercept)

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