Algebra 1 Common Core Student Edition, Grade 8-9

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 ® 3 relate s 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.

12. y 8 w hen ■


13. y 3 when =
    
    
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         13. y 15 when * 6.
         
         
         
         
      
      
      5. y * - 4 w hen » 4.
         For th e da ta in each table, tell w hether y varies directly
         w ith . If it does, write a n eq uation for the direct variation.
      
      
      
      
    
    
    
    


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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