__More Slope__

More slope...well...there *is* more...

**BIG RULE: **PARALLEL LINES HAVE THE SAME SLOPE

PERPENDICULAR LINES HAVE NEGATIVE RECIPROCAL OF THE OTHER'S SLOPE

**ALSO BIG RULE: **Horizontal lines have *0 slope*, because the
change in y will be 0, and whatever the change in x is, 0 divided anything is 0.

Vertical lines have *undefined slopes*, because the change in x will be
0, and whatever the change in y is, anything divided by 0 is undefined.

Now for a vocabulary word...

__y-intercept:__ y coordinate when the line crosses
the y-axis (when x = 0)...commonly denoted using "b"

For example, let us make the graph of **x - y = 1**

**x - y = 1
-y = 1 - x
(-1)-y = (-1)1 + (-1)-x
y = x - 1**

__x | y
__0 | -1

1 | 0

2 | 1

As you can see, the line crosses the y-axis at (0,-1), so the y-intercept is -1.

*********

BIG EQUATION::::::

**y = mx + b**

**in which m is the slope of the line and b is the
y-intercept**

So...we had changed **x - y = 1** to slope equation form where it was **y
= x - 1**

if there is no coefficient on x, it is a 1, so using that form, m = 1 and b = -1

We already graphed it, so we know this is true (check the slope if you don't believe me *_*)

Now...we didn't even have to make a table of values if we knew this. We would just make a point at (0,-1) because we know that is the y-intercept. Then we would use the slope to make another point. We'd go 1 to the right and 1 up, or 1 to the left and 1 down, or 2 to the right and 2 down, etc. In any way, it will give another point on the line. If you want a third point, just do it again, and connect the points.

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