Algebra Know-It-ALL

by moving to the right by Δy= 4 units and upward by Δx= 3 units. The slope is

therefore

m=Δx/Δy

= 3/4

Remember that the slope of a line is the ratio of a change in the dependent variable to the

change in the independent variable. That means the slope is now Δx/Δy, not Δy/Δx. We

have determined the slope and the x-intercept for line L*, so we can write its SI equation as

x= (3/4)y− 3

6. In part D of Fig. B-8, line M* passes through (−2, 0) and (0, −3). The x-intercept is −3.
   When we go from (−2, 0) to (0, −3), we move to the right by Δy= 2 units and upward
   by Δx=−3 units (the equivalent of downward by 3 units). The slope is therefore

m=Δx/Δy

=−3/2

(0,4)

(0,–2)

x

y

LM

(–3,0)

(0,4)

(0,–2)

x

y

(–3,0) LM

(0,4)

(0,–2)

x

y

LM(–3,0)

A B

C D

Each axis

increment

is 1 unit

M*

L*

(0,–3)

(4,0)

(–2,0)

x

y

Figure B-8 Illustration for the solutions to Probs. 4 through 7 in

Chap. 17. (The rotated and reversed characters are

not typos! The text explains this.)

Chapter 17 647