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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 27 Page 312

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

y=5/2x-1/2

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.

We can see that the function intercepts the y-axis at ( 0, - 12). This means that the value of b is - 12. y= mx+( -1/2)

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.

Here we have identified (1,2) 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,- 1/2) & ( 1,2)

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

a-(- b)=a+b

m=2+1/2/1-0

Write as a fraction

m=2/1+1/2/1-0

a/b=a * 2/b * 2

m=4/2+1/2/1-0

Add fractions

m=5/2/1-0

Subtract term

m=5/2

The value of the slope m is 52.

Writing the Equation

Now that we have the slope and the y-intercept, we can write our final equation. y= 5/2x+( -1/2) ⇔ y=5/2x-1/2

Subchapter links

Lesson Check p.311

Practice and Problem-Solving Exercises p.312-314

Standardized Test Prep p.314

Mixed Review p.314