Big Ideas Math: Modeling Real Life, Grade 8
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7. Writing Equations in Point-Slope Form
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Exercise 15 Page 183

Point-slope form is y-y_1=m(x-x_1).

y=2x

Practice makes perfect
Equations in point-slope form follow a specific format. y- y_1= m(x- x_1) In this form, m is the slope of the line and ( x_1, y_1) is a point on the line. Here, we are given that the line passes through two known points. (2,4) and (3,6) To determine the slope of the line, we use the Slope Formula.
m=y_2-y_1/x_2-x_1
m=6- 4/3- 2
m=2/1
m= 2
Now that we know the slope of the line is 2, we can write the equation of the line in point-slope form. We can use either of the given points as (x_1,y_1) in our equation. Let's use ( 2, 4).
y-y_1=m(x-x_1)
y- 4= 2(x- 2)
Since any point on the line could be used to form a point-slope equation, there are infinitely many possible equations. However, we are asked to write the equation in slope-intercept form, so this will give us a unique equation for this line.
y-4=2(x-2)
y-4=(2)x-(2)2
y-4=2x-4
y-4+4=2x-4+4
y=2x