# data[].attributes.attachment_link.description
Subtracting polynomials works almost exactly the same way as does adding polynomials. This lesson demonstrates both vertical and horizontal subtraction of polynomials, and demonstrates how to keep track of those "minus" signs.

# data[].attributes.attachment_link.readable_text
The "point-slope" form of the equation of a straight line is:

The equation is useful when we know:

and want to find other points on the line.

Have a play with it first (move the point, try different slopes):

Now let's discover more.

What does it stand for?

m is the slope of the line

(x, y) is any other point on the line

Making sense of it

It is based on the slope:

Starting with the slope:

we rearrange it like this:

to get this:

So, it is just the slope formula in a different way!

Now let us see how to use it.

Example 1:

That is a perfectly good answer, but we can simplify it a little:

Example 2:

We can pick any point for , so let's choose (0,0), and we have:

y − 0 = −3(x − 0)

Which can be simplified to:

Example 3: Vertical Line

What is the equation for a vertical line?
The slope is undefined!

In fact, this is a special case, and we use a different equation, like this:

Every point on the line has x coordinate 1.5,
that's why its equation is x = 1.5

What About y = mx + b ?

You may already be familiar with the " y=mx+b" form (called the slope-intercept form of the equation of a line).

It is the same equation, in a different form!

The "b" value (called the y-intercept) is where the line crosses the y-axis.

and the equation becomes:

# data[].attributes.attachment_link.description
The equation is useful when we know: and want to find other points on the line. Have a play with it first (move the point, try different slopes): Now let's discover more.

# data[].attributes.attachment_link.title
Point-Slope Form;  Writing Equations in Point-Slope Form Given Two Points