How the Slope & Y-Intercept Effect a Line

Ms. MankelAlgebra

What Happens to the Slope?

The steepness, or slant, of a line is called the slope.

Use the website and think about it… What happens to the line when the slope

increases? What happens to the line when the slope is

a fraction?

Explore

Let’s Compare Slopes

Click here -Scroll down to ‘Slippery Slopes’Write down 3 things you notice.

Remember Writing Equations?

The type of equation we were writing was called Slope-Intercept Form.

y=mx+b, m is the slope b is the y-intercept

More About Slope-Intercept Form

Recall that the y-intercept is where the line intercepts, or crosses, the y-axis (vertical) This also happens to be the value of y when x=0

Recall that slope is the steepness of the line.

Let’s Play with the Numbers

How does changing the m value (slope) change the way the line looks?

How does changing the b value (y-intercept) change the way the line looks?

Explore Scroll down to ‘Interactive Slope Intercept From

What about Positive Slope?

Notice that when the slope, m, is positive, the line slants _______ to the right.

The more positive m is, the _______the line will slant upward to the right.

What about Negative Slope?

When the slope is negative, the line slants _________ to the right, and, as the slope becomes more and more negative, the line will slant downward __________ to the right.

When the y-intercept, b, is positive, the line crosses the y-axes ______ y = 0. When b is negative, the line crosses the y-axis somewhere ______ y = 0.

What about b (y-intercept)?

3.5 Slope

To determine if slope is positive or negative, look at the line from left to right (just like you read).

Down …negative. UP…positive.

Find Slope from a Graph

Choose two pointsStarting with the point located farther left, you will travel to the point farther right.You MUST travel in a ‘L’ shape.First travel up or down, then travel right or left.Let’s see someone do that. Scroll down to the graphs

12

12

xx

yym

Formula for SlopeA way to remember which value goes on top.

2Y 1-Y2X 1- X

Keep the pairs together.

Understand???

Let’s work on a few problems to see if we understand.