`Acing the Test`

Doing well on tests, whether they are chapter

tests o r state assessm ents, d e p e n d s o n a d e e p

understanding o f math concepts, fluency with

calculations and com putations, and strong

problem -solving abilities.

`All of these opportunities for practice`

help you prepare for assessments

th ro u g h o u t the y e a r inclu d in g

the assessm ents to m easure y o u r

proficiency with the

Common Core

State Standards.

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5-2 Direct Variation

`TIPS FOR SUCCESS`

Some questions on standardized

tests ask you to use a graph.

Read the sample question at

the right. Then follow the tips to

answer it.

TIP 1

Identifying the y-intercept may

help eliminate some possibilities.

`What is an equation of the line shown`

below?

`C7D y * f * - 1`

>y* 3*

`CO y = 3* - 1`

`TIP 2`

Find the slope by using the point that represents the

y-intercept and another point on the line.

`Think I f Through`

You can see from die graph that

the y-intercept is - 1. So you

can eliminate choices B and D.

To get from (0, - 1 ) to (1,2),

move3 units up and 1 unit to

die right. The slope is f = 3. So

an equation is y ** 3* - 1. The

correct answer is C.

`<0 Vocabulary Buiidor`

k Review

tio n represents a d irec t v ariatio n If it has the form

x, where k * 0. The coefficient k is the co n s ta n t

iation.

ipie

tse y varies directly with *, and y = 15 w h e n * = 5.

a direct variation equation th at relates * and y. W hat
value ofy w h e n * = 9?

= kx Start with the general form of a direct variation.

= k{ 5) Substitute 5 for x and 15 for y.

» k Divide each side by 5 to solve for k.

= 3

*Write an equation. Substitute 3 for k in y = kx.*

(uationy ® 3relate s

(uationy ® 3

*a n d y .W h e n*= 9 ,y = 3(9),

`Exercises`

Suppose y varies direcdy with *. Write a direct variation

equation th at relates * and y. Then find th e value of y when

* = 7.

- y
*8 w hen*■ - y
*3 when*=

- y
*15 when** 6.

- y
- y *
*- 4 w hen**» 4.*. If it does, write a n eq uation for the direct variation.

For th e da ta in each table, tell w hether y varies directly

w ith

ISIS -1 -6 C M-3 7.

2 3 - 1 2.

512 2-

9 24 5 -1 2 5

`At the end of the chapter, you'll find a Quick R©vi©W`

of the concepts in the chapter and a few examples and

exercises so you can check y o u r skill a t solving problem s

related to the concepts.

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`In th e C u m u la tiv e S ta n d a rd s R e v ie w`

at the end of the chapter, you'll

also find Tip s f o r Su ccess,

rem inders to help w ith problem

solving. W e include problem s of all

different formats and types so you

can feel com fortable w ith any test

item o n y o u r state assessm ent.

`Using Your Book f or Success xvii`