How do you find slope-intercept form of the equation for a line?

Question

there is a graph with a line going through points (-1,-4) and (1,2).
I'm just SO confused on how to do this!!!

Answer 1

That's not so hard. Slope-intercept form is Y=Mx+B. B is where the line goes through the Y-axis (the line that goes up and down). Mx is the slope, which can be found by dividing rise by run. Rise is whether the line goes up or down (in this case, up). Run is how the line goes to the right (it always goes to the right, whether up or down). In this case, the lines Rises by 6, and the line Runs by 2. 6 divided by 2 is 3.

So, Y=3x-1. And I solved this problem by drawing it out, that's how I know. Well, technically, I drew it roughly in about five seconds, so it might not be an _exact_ -1.

Hope that helps.

Answer 2

Ok now unless I am much mistaken (And I hope I'm not considering I have a Math Final this week) Slope-Intercept form in is the form of Y=Mx+B So wtf does that mean? Well the M is your slope, to gind slope you simply need to do the following equation Y2-Y1/X2-X1

Now the Ys and Xs come from your two points you have, so now that you have your slope the B is the Y-intercept of the equation, To find this I recommend using a graphing calc. But if you don't have one you can always plug in 1 of your ordered pairs and solve for B, So your example:

2-(-4)=6 and 1-(-1)=2 so your slope is 6/2 which simplifies to 3

Y=3X+B now you plug in on of the ordered pairs (I'm going to use (1,2)) 2=3(1)+B
subtract the 3 to get -1=B which means the Y-intercept is (0,-1) so your equation is Y=3x-1

-Ferret

Answer 3

There are a couple of ways. Both involve calculating the slope by using slope = change in y over change in x

Here that is (2 - -4)/(1 - -1) which comes out 6/2 = 3.

Method 1: Plug directly into y = mx + b by choosing either point and replacing x and y with its coordinates, putting in m, and solving for b:

2 = 3(1) + b

2 = 3 + b

-1 = b

So y = 3x - 1

Method 2: use point-slope form and then get y by itself:

y - y1 = m(x - x1) where (x1, y1) is a point on the line

y - 2 = 3(x - 1)
y - 2 = 3x - 3

add 2 to both sides: y = 3x - 1

I hope one or both makes sense - send an IM if you wish and I will explain more

Answer 4

slope intercept form is y=mx+b
(m is the slope and b is the y intercept)

m= (y2-y1)/(x2-x1) so you just plug in the numbers you have
m= [2-(-4)]/[1-(-1)] or 6/2 or 3 (all are the same thing)

so now you use any two of the points you want to figure out b. i'll use (1,2).
2=3(1) + b (slove the eqation)
2=3+b
-1=b

so to write it in slope intercept form you would write y=3x - 1

hope that was clear. good luck with the rest of your problems!