Algebra Know-It-ALL

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.

10. 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

1. 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