  ## y-intercept: The Start of Your Line

The y-intercept of a line is nothing more than an ordered pair.  The only special thing about the y-int is that the x-value must be zero.

 Examples: (0, 5) (0, 3) (0, -4) (0, 18)

Notice the common trend, the first number (x) is always 0.

 Finding the y-intercept from an Equation

To find the y-int, plug in x = 0 for your equation, and solve for y.

 Example: y = 4x + 3 y = 4(0) + 3 plug in x = 0 y =  0 + 3 y = 3 solve for y (0, 3) write the point as (0, y)

Instead of writing the y-int as (0, 3), we can also write it as...

y - intercept = 3, or for short, y-int = 3.

The y-intercept is also often written as b = 3.  We use the letter b to represent the beginning of the line.  We use this to help us graph a line in the coordinate plane.

 Finding the y-intercept from a Table of Values

A table of values is a list of ordered pairs written as a table...

 x 0 1 2 3 4 y 2 4 6 8 10

We want to find the place where x = 0.  The matching y value right below there is our y-intercept.  Take a look... y-int = 2

Sometimes the value where x = 0 will not be shown in the table.  In this situation, you will need to continue the pattern until you find x = 0.

 x 2 4 6 8 10 y 5 8 11 14 17

Continue the pattern... I knew that the numbers to the left had to be 0 and 4 because I continued the pattern of adding 2 and adding 3.  The y-int = 4.

 Finding the y-intercept from a Graph

The y-int from a graph is still the y value where x = 0.  Luckily, there is a really easy way to find it.  Just look for the place where your line crosses the y-axis.

Look for yellow and blue lines to make a green dot... The y-int is the green dot shown above.  The x-value is 0, and the y-value is 1.  That is why the point is (0, 1).

The y-intercept is often paired with slope.  Learn how to graph using the slope and y-intercept or take a look at slope intercept form.