Algebra Know-It-ALL

334 Review Questions and Answers

left side of the equals sign. In Answer 16-4, that was done starting with the original equation. If

we start with the SI form with y as the dependent variable, we can do this:

y= (1/3)x+ 3

y− 3 = (1/3)x

3 y− 9 =x

x= 3 y− 9

This SI equation tells us that the x-intercept is equal to −9.

Question 17-6

How can we morph Fig. 20-6, the graph of the system from Question and Answer 17-1 and

Fig. 20-6, to get a graph that will show the same system with y as the independent variable

andx as the dependent variable?

Answer 17-6

We can use the rotate-and-mirror method. We start with Fig. 20-6 and rotate the entire

assembly as a single mass—axes, lines, and points—counterclockwise by a quarter-turn (90°).

Then we mirror the whole thing left-to-right. Finally, we reverse the ordered pairs to obtain

the new points. The result is shown in Fig. 20-7.

Question 17-7

What are the SI forms of the equations for the lines in Fig. 20-7?

Solution =

(2,–3)

(3,0) (8,0)

Each axis

increment

is 1 unit

x

y

Figure 20-7 Illustration for Questions and Answers

17-6 through 17-10.