Point-Slope Form

Point-Slope Form

Point-Slope Equations need 2 things....

• A point

• A slope

Multiple Choice

Which of these is point-slope?

• $y-y_1=m\left(x-x_1\right)$

• $y=mx+b$

• $Ax+By=C$

Multiple Choice

Write an equation of the line going through the point (-4, 1) with a slope of 1/3.

• $y-1=\frac{1}{3}\left(x+4\right)$

• $y+4=\frac{1}{3}\left(x-1\right)$

• $y-4=\frac{1}{3}\left(x+1\right)$

• $y+1=\frac{1}{3}\left(x-4\right)$

What if I'm given just 2 points?

• Use the slope formula to calculate the slope

•  $\frac{y_2-y_1}{x_2-x_1}$  

• Choose ONE of the points

• Substitute the values of your chosen point and the slope calculated into the Point-Slope form

Multiple Choice

Write the equation in point-slope form for the line that contains the points

(-2, -3), (4, 3)

• y - 3 = 1(x - 2)

• y + 3 = 1(x + 2)

• y -3 = -1(x + 2)

• y + 3 = -1(x - 2)

We also learned how to transform Point-Slope equations into Slope Intercept form.

Poll

Is this slope intercept form?

 $2y\ =4x\ +10$  

• yes because it's $y=mx+b$   

• no, because there is a coefficient on the y.  You need to divide the entire equation by 2 first in order to get  $y=mx+b$  

Poll

How ready for this weekly recap are you?