Expert: Richard J. Raridon - 8/9/2010

Question
If given the set of two ordered number pairs (4,3) and (8,4) how do you get the right equation in the form of 4y-x=8 (if this equation is correct). It would be something like this. Also could you please do the same with (1,-2) and (2,-6) and how do you get these equations in these forms

Answer
One standard equation form is the slope-intercept form, y = mx+b
where m is the slope and b is the y-intercept.  You can evaluate m and b by putting in data for two points.  For your first set,
3 = m(4)+b and 4 = m(8)+b.  solve for m and b to get m=1/4 and b=2.
So your equation is y = (1/4)x+2 or 4y = x+8 (what you got).  
For the second set, -2 = m(1)+b and -6 = m(2)+b. So m=-4, b=2 and your equation is y = -4x+2, or 4x+y = 2