which simplifies to
y− 8 = (x− 2) × (−12) / (−2)
and further to
y− 8 = 6(x− 2)
That’s the PS form of the equation.
- Once again, here’s the general two-point equation:
y−y 1 = (x−x 1 )(y 2 −y 1 ) / (x 2 −x 1 )
This time, we’re told that (−6,−10) and (6, −12) lie on the graph. Let’s assign x 1 =−6,
x 2 = 6, y 1 =−10, and y 2 =−12. When we plug in these numbers, we get
y− (−10)= [x− (−6)][− 12 − (−10)] / [6 − (−6)]
This “nightmare of negatives” simplifies to
y+ 10 = (x+ 6) × (−2) / 12
and further to
y+ 10 = (−1/6)(x+ 6)
We want the SI form, so we have a little more manipulation to do. Applying the distribu-
tive law of multiplication over addition to the right side, we get
y+ 10 = (−1/6)x− 1
Subtracting 10 from each side produces the desired result:
y= (−1/6)x− 11
That’s the SI form of the equation.
Chapter 16
- Let’s call the numbers x and y. We’re told that both of the following facts are true:
x+y= 44
and
x−y= 10
Chapter 16 637