Question 259531
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