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 19 Page 319

Start by finding the slope.

Point-Slope Form: y-4=3/2(x-1)

Slope-Intercept Form: y=3/2x + 5/2

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=1- 4/- 1- 1
m=- 3/- 2
m=3/2
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= 32. 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 ( 1, 4). y- 4= 3/2(x- 1) 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= 32 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 ( 1, 4) one more time.
y=3/2x+b
4=3/2 ( 1)+b
â–Ľ
Solve for b
4=3/2+b
4-3/2=b
8/2-3/2=b
5/2=b
b=5/2
Now that we know the y-intercept is 52, we can write the slope-intercept form of the line. y=3/2x+ 5/2