Big Ideas Math: Modeling Real Life, Grade 8
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7. Writing Equations in Point-Slope Form
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Exercise 16 Page 183

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

y=x+5

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. (-2,3) and (2,7) To determine the slope of the line, we use the Slope Formula.
m=y_2-y_1/x_2-x_1
m=7- 3/2-( -2)
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Simplify right-hand side
m=7-3/2+2
m=4/4
m=1
Now that we know the slope of the line is 1, 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, 3).
y-y_1=m(x-x_1)
y- 3= 1(x-( -2))
y-3=1(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-3=1(x+2)
y-3=(1)x+(1)2
y-3=x+2
y-3+3=x+2+3
y=x+5