# math

posted by
**mathstudent**
.

Show that the formula for a line through two points (a1,b1) and (a2,b2) is:

y=(b1-b2)/(a1-a2) * x + (a1*b2-a2*b1)/(a1-a2)

The slope part looks right. Could someone explain how the y-intercept part makes sense?

I would think that the y-intercept is:

b1-slope*a1

or

b2-slope*a2

anyone have any ideas?