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

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2 Answers

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
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