Things About A Graph

Things About a Graph…

y

Where a line crosses the X- axis is called the XIntercept X

X-intercept = -1

y

Same thing with the Y axis. x

y-intercept = 2

y

• What are the X and Y intercepts? X-Intercept = -3

x

Y-Intercept = 4

y = 3x + 1 If you just have a function without a graph, you can still find the X and Y intercepts!

WOW!!

• To find the xintercept, just sub in a 0 for y in the formula…. …and solve for X!

y = 3x + 3 (0) = 3x + 3 +(-3)

+(-3)

-3 = 3x 3

3

x-intercept is -1 -1 = x

To find the y-intercept just sub in 0 for x

…and solve for y !

y = 3x + 3 y = 3(0) + 3

y=3 Whoa, we’re done! Y-intercept is 3

CLASSWORK: Find the X and Y intercepts of the following functions: 3. y = 3x + 12 4. 6x + 3y = 24 5. x = 2y + 4

Mr. A will help you over here…

CONGRATULATIONS!!!!!!!! Now that you have the X & Y intercepts, you can graph these without having to do that crazy function chart!!!! LET’S GRAPH ‘EM !!!!

The slope of a graph is a measure of how steep it is. The bigger the number, the steeper the slope

slope is only This line is This perfectly flat. about What think the¼slope is? This linedo is you REALLY STEEP!! The slope here is 0about 10000000 !

This slope is exactly 1 Okay, maybe just 20…that’s still steep!

A line that goes up from left to right has a positive slope. POSITIVE SLOPE !

BARELY POSITIVE! (almost ZERO!)

NOT POSITIVE! must be… NEGATIVE SLOPE!

Lines that go down from left to right have NEGATIVE SLOPES

In Math, the slope of a line is:

SLOPE =

DIFFERENCE IN Y DIFFERENCE IN X

How to find the SLOPE. • Pick any two points of the line • Find the difference in Y and write it. • Find the difference in X and write it under. • Simplify the fraction, and that’s the slope!!

+2 +3

Or do it with math!

(-3,3)

•

Pick two points, and get their coordinates. • Difference in y Difference in x (remember: “difference” means you substract!)

3 – (-3) Slope = -3 – 1 =

(1,-3)

6 -4

-3 = 2

What’s the slope?

Here are two points on a line. What is the slope? (3,6)

(-5,-7)