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Big Ideas Math: Modeling Real Life, Grade 8

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Big Ideas Math: Modeling Real Life, Grade 8 View details

Practice Test

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Exercise 9 Page 192

First, use the given points to calculate the slope. Then, identify the y-intercept.

y=- 4/3x-1

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 given graph.

Slope

Let's start by substituting the points given on the graph into the Slope Formula and calculating m.

m = y_2-y_1/x_2-x_1

SubstitutePoints

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

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

▼

Simplify right-hand side

Subtract term

m=-4/0-(- 3)

a-(- b)=a+b

m=-4/0+3

Add terms

m=-4/3

MoveNegNumToFrac

Put minus sign in front of fraction

m=-4/3

We calculated that the slope of the given equation is - 43. Now, let's calculate the y-intercept and then write the equation in slope-intercepted form.

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, - 1). This means that the value of b is - 1.

Writing the Equation

Now that we have the slope and the y-intercept, we can write our final equation. y= - 4/3x+( - 1) ⇔ y=- 4/3x-1

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