Big Ideas Math: Modeling Real Life, Grade 8
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2. Solving Systems of Linear Equations by Substitution
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Exercise 12 Page 207

Does either of the equations have an isolated variable in it?

(3,0.5)

Practice makes perfect

In this system of equations, neither of the equations has an isolated variable. Therefore, we can determine the solutions by graphing the given equations. To do this, we will need the equations to be in slope-intercept form to help us identify the slope m and y-intercept b.

Write in Slope-Intercept Form

Let's rewrite each of the equations in the system in slope-intercept form, highlighting the m and b values.

Given Equation Slope-Intercept Form Slope m y-intercept b
0.5x+y=2 y= - 0.5x+ 2 - 0.5 (0, 2)
0.5x=1+y y= 0.5x+( - 1) 0.5 (0, - 1)

Graphing the System

To graph these equations, we will start by plotting their y-intercepts. Then, we will use the slope to determine another point that satisfies each equation, and connect the points with a line.

We can see that the lines intersect at exactly one point.

The point of intersection at (3,0.5) is the one solution to the system.