A linear equation is one that relates the first power of two variables, x and y, and its graph is always a straight line. The standard form of such an equation is

Ax + By + C = 0

where A, B and C are constants.

Every straight line has slope, usually designated by the letter m. Slope is defined as the change in y divided by the change in x between any two points (x_{1}, y_{1}) and (x_{2}, y_{2}) on the line.

## Sciencing Video Vault

m = ∆y/∆x = (y_{2} - y_{1}) ÷ (x_{2} - x_{1})

If the line passes through point (a, b) and any other random point (x, y), slope can be expressed as:

m = (y - b) ÷ (x - a)

This can be simplified to produce the slope-point form of the line:

y - b = m(x - a)

The y-intercept of the line is the value of y when x = 0. The point (a, b) becomes (0, b). Substituting this into the slope-point form of the equation, you get the slope-intercept form:

y = mx + b

You now have all you need to find the slope of a line with a given equation.

## General Approach: Convert from Standard to Slope-Intercept Form

If you have an equation in standard form, it takes just a few simple steps to convert it to slope intercept form. Once you have that, you can read slope directly from the equation:

## Write the Equation in Standard Form

Ax + By + C = 0

## Rearrange to Get y by Itself

By = -Ax - C

y = -(A/B)x - (C/B)

## Read Slope from the Equation

The equation y = -A/B x - C/B has the form y = mx +b, where

m = -(A/B)

## Examples

**Example 1:** What is the slope of the line 2x + 3y + 10 = 0?

In this example, A = 2 and B = 3, so the slope is -(A/B) = -2/3.

**Example 2**: What is the slope of the line x = 3/7y -22?

You can convert this equation to standard form, but if you're looking for a more direct method to find slope, you can also convert directly to slope intercept form. All you have to do is isolate y on one side of the equal sign.

## Add 22 to Both Sides and Put the y Term on the Right

3/7y = x + 22

## Multiply Both Sides by 7

3y = 7x + 154

## Divide Both Sides by 3

y = (7/3)x + 51.33

This equation has the form y = mx + b, and

**m = 7/3**