SOLUTION: This is supposed to be review, so I feel kind of stupid, but i forgot how to do point-slope form. Well... here's my problem: Write the point-slope form of the equation of the li

Algebra ->  Graphs -> SOLUTION: This is supposed to be review, so I feel kind of stupid, but i forgot how to do point-slope form. Well... here's my problem: Write the point-slope form of the equation of the li      Log On


   

Question 259531: This is supposed to be review, so I feel kind of stupid, but i forgot how to do point-slope form. Well... here's my problem:
Write the point-slope form of the equation of the line through the given points.
Through: (0,-1) and (3,1)
I have more of these, so I only want one answer so i can know how to do the rest... Thank You!!
Found 2 solutions by mathbath, Edwin McCravy:
Answer by mathbath(13) About Me  (Show Source):
You can put this solution on YOUR website!
If (x1,y1) and (x2,y2) are any two co-ordinates on the line the slope "m" of the line is calculated by,
m=(y2-y1)/(x2-x1)
Substituting the values from the given problem..
(x1,y1) = (0,-1)
(x2,y2) = (3,1)
So,
m = (1 - (-1))/(3 - 0)
m = (1 + 1)/(3)
m = 2/3
Now the standard equation for a straight line is..
y=mx+c --> (1)
where m is the slope
and c is the y-intercept of the line i.e., when the line hits the y-axis and x = 0
If you notice the co-ordinate (0,-1) ..
x = 0, y = -1
This is the co-ordinate where the line intersects the y-axis. So our y intercept is -1
So,
c = -1
Substituting the values in (1)
y = 2/3x - 1 which is the point slope form of the equation

Answer by Edwin McCravy(20064) About Me  (Show Source):
You can put this solution on YOUR website!
I need help with this problem: What is the standard form of an equation form of that passes through (3,0)and (6,-8). 


Use the slope formula:

    y2 - y1
m = —————————
    x2 - x1

where (x1, y1) = (0,-1) and (x2, y2) = (3,1)  

     (1) - (-1)     2     
m = ———————————— = ——— = 2%2F3
     (3) - (0)      3     

Now substitute in the point slope formula:

  y - y1 = m(x - x1)

  y - (-1) = 2%2F3(x - 0)

    y + 1  = 2%2F3x

        y  - 2%2F3x - 1

Here's the graph:



Edwin