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Pearson Algebra 1 Common Core, 2011

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Pearson Algebra 1 Common Core, 2011 View details

3. Slope-Intercept Form

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Exercise 23 Page 312

Identify the y-intercept. Then, find another point that lies on the grid.

y=2x-3

Practice makes perfect

Equations written in slope-intercept form follow a specific format. y= mx+ b In this form, m is the slope and b is the y-intercept. We need to identify these values using the graph.

y-intercept

The y-intercept is the y-value where the line crosses the y-axis.

y-intercept

We can see that the function intercepts the y-axis at (0, - 3). This means that the value of b is - 3. y= mx+ - 3

Slope

To find the slope, we will trace along the line on the given graph until we find a lattice point, which is a point that lies perfectly on the grid lines.

Finding a Lattice Point

Here we have identified (2,1) as our second point. We will now substitute the points into the Slope Formula and calculate the slope.

m=y_2-y_1/x_2-x_1

SubstitutePoints

Substitute ( 0,- 3) & ( 2, 1)

m=1 - ( - 3)/2- 0

a-(- b)=a+b

m=1+3/2-0

Add and subtract terms

m=4/2

Calculate quotient

m=2

The value of the slope m is 2.

Writing the Equation

Now that we have the slope and the y-intercept, we can write our final equation. y= 2x+( - 3) ⇔ y=2x-3

Subchapter links

Lesson Check p.311

Practice and Problem-Solving Exercises p.312-314

Standardized Test Prep p.314

Mixed Review p.314