find the slope intercept form of the equation of the line through the points (-4,2) and (0,-5)

Question

Js there a formula? is it y2-y1 divided by x2-x1??

Answer 1

Hi Gina,

 

You are close. The formula you listed is the formula to find the slope of the line. By plugging in values from the two points, it becomes:

 

-5 - 2    -7

------ =  --

0 - -4     4

 

So, -7/4 is the slope of the line. Recall that the slope-intercept form is y = mx + b, where m is the slope, and b is the y-intercept. So now that you know the slope, you have:

 

y = -7/4x + b

 

To find b, use either of your two given points and plug the x and y values into your equation. Lets use (-4,2), so x is -4 and y is 2:

y = -7/4x + b

2 = -7/4(-4) + b

2 = 7 + b

-5 = b

 

So the final equation is:

 

y = -7/4x - 5

 

Double check by plugging in values from your second given point, (0, -5):

-5 = -7/4(0) - 5

-5 = -5

Answer 2

a)

 

Y = mx +b

   

   m = slope       ( Y2 - Y1) / (X2 - X1)= ( 2- (-5) ) / ( -4 -0) = -7/4

 

    Y = -7/4 x + b

 

    The coordinates of points should work:

 

       -5 = 0(X) + b

      

        b =- 5

 

    Y = -7/4 x- 5      ./equation of the line.

 

  b)

 

   7X + 4y =-20     ? in standard form