Pearson Algebra 1 Common Core, 2011
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Pearson Algebra 1 Common Core, 2011 View details
4. Point-Slope Form
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Exercise 20 Page 319

Find the slope of the line that connects the points.

Point-Slope Form: y-4=2(x-2)
Slope-Intercept Form: y=2x

Practice makes perfect
To write both the slope-intercept and the point-slope form equations, we need to find the slope of the line. To do so, we will substitute the given points into the Slope Formula.
m=y_2-y_1/x_2-x_1
m=- 6- 4/- 3- 2
m=- 10/- 5
m=10/5
m = 2
Now, let's form our equations.

Point-Slope Form

Let's recall the general form of a point-slope equation.

y- y_1= m(x- x_1) Here, m is the slope and ( x_1, y_1) is a point on the line. We already calculated the slope m= 2. We have also been given two points on the line. Since we only need one point to write the point-slope equation, let's use ( 2, 4). y- 4= 2(x- 2) Please note that any point on the line can be used to form a point-slope equation. Therefore, our equation is only one of infinitely many possible equations!

Slope-Intercept Form

Let's recall the general form of a slope-intercept equation. y= mx+ b Here, m represents the slope and b represents the y-intercept. We already calculated the slope m= 2 above. The next step is substituting one of the points in the equation and then solving for the y-intercept b. Let's use the point ( 2, 4) one more time.
y=2x+b
4=2 ( 2)+b
â–Ľ
Solve for b
4=4+b
4-4=b
0=b
b=0
Now that we know the y-intercept is 0, we can write the slope-intercept form of the line. y=2x+ 0 ⇔ y=2x