SOLUTION: I am given to sets of points (-2,-4) and (2,1). I need to write an equation. this is what I did: m= 1- (-4)/2- (-2) = 3/0 = 3 y= 3x + b -4 = 3(-2) + b -4 = -6 + b +6 +6

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: I am given to sets of points (-2,-4) and (2,1). I need to write an equation. this is what I did: m= 1- (-4)/2- (-2) = 3/0 = 3 y= 3x + b -4 = 3(-2) + b -4 = -6 + b +6 +6       Log On


   

Question 184999This question is from textbook
: I am given to sets of points (-2,-4) and (2,1). I need to write an equation.
this is what I did:
m= 1- (-4)/2- (-2) = 3/0 = 3
y= 3x + b
-4 = 3(-2) + b
-4 = -6 + b
+6 +6
-2=b ???????
Very Confusing This question is from textbook

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Start with the general linear equation in the "slope-intercept" form:
y+=+mx%2Bb
Find the slope from the given points (-2,-4) (2,1) using:
m+=+%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29 and the (x%5B1%5D,y%5B1%5D) are the x- and y-coordinates of the first point. Similarly for the second point, so...
m+=+%281-%28-4%29%29%2F%282-%28-2%29%29
m+=+5%2F4 Now plug this into the general equation we had at the start.
y+=+%285%2F4%29x%2Bb Now we need to find the value of b, the y-intercept. This is done by substituting the x- and y-coordinates of either one of the two given points. Let's use the second point (2,1).
y+=+%285%2F4%29x%2Bb Substitute x = 2 and y = 1 and solve for b.
1+=+%285%2F4%29%282%29%2Bb
1+=+5%2F2+%2B+b Subtract 5%2F2 from both sides of the equation.
%282%2F2%29-%285%2F2%29+=+b Simplify.
b+=+-3%2F2 Now you can write the final equation in slope-intercept form:
highlight%28y+=+%285%2F4%29x-3%2F2%29
A few comments on your work.
It seems that you are having trouble handling the addition/subtraction of positive/negative integers.
Remember...to subtract an integer, you add its additive inverse (opposite), thus:
1-%28-4%29+=+1%2B%284%29=5 and
2-%28-2%29+=+2%2B2=4
Furthermore, you came up wth a slope m+=+3%2F0 but remember, if a fraction has a zero in the denominator, it considered "undefined" because division by zero is not defined in mathematics.