Slope-Intercept Form
Find the slope between two points:
y = mx + b
For the points (x1, y1) and (x2,y2) use the formula
𝑦 −𝑦
where m = slope and b = y-intercept
m = 𝑥2 − 𝑥1
2
1
What slope means
Direct Variation
Slope is how steep a line is.
When y varies directly to x, we know that
Positive slope = line slants UP
Negative slope = line slants DOWN
y = ax
where “a” is the constant of variation.
How to find slope given an equation
How to find slope given a graph
Get y by itself first.
Pick two points on the graph.
Make sure it’s in y = mx + b form.
The number in front of the x is slope.
Count how many you have to move up/down (this
goes on top of a fraction), then how many you
move left/right (bottom of the fraction)
Finding the constant of variation
Simplify.
Finding the equation of a line given a graph
If y varies directly to x, write down y = ax
Look where the line crosses the y – axis. This is the
b in y = mx + b.
Plug in the numbers they give you for x and y
Get “a” by itself.
HOYVUX
Stands for
Horizontal lines have 0 slope and have equations
that look like Y = a number.
Vertical lines have Undefined slope and have
equations that look like X = a number.
Pick two points on the line and determine the
slope. This is the m in y = mx + b.