<< Chapter < Page Chapter >> Page >

Solve 3 ( m 6 ) 2 m = 4 + 1 for m .

3 ( m 6 ) 2 m = 4 + 1 3 m 18 2 m = 3 m 18 = 3 m = 15

C h e c k : 3 ( 15 6 ) 2 ( 15 ) = 4 + 1 Is this correct? 3 ( 9 ) 30 = 3 Is this correct? 27 30 = 3 Is this correct? 3 = 3 Yes, this is correct .

Got questions? Get instant answers now!

Practice set b

Solve and check each equation.

16 x 3 15 x = 8 for x .

x = 11

Got questions? Get instant answers now!

4 ( y 5 ) 3 y = 1 for y .

y = 19

Got questions? Get instant answers now!

2 ( a 2 + 3 a 1 ) + 2 a 2 + 7 a = 0 for a .

a = 2

Got questions? Get instant answers now!

5 m ( m 2 a 1 ) 5 m 2 + 2 a ( 5 m + 3 ) = 10 for a .

a = 10 + 5 m 6

Got questions? Get instant answers now!

Often the variable we wish to solve for will appear on both sides of the equal sign. We can isolate the variable on either the left or right side of the equation by using the techniques of Sections [link] and [link] .

Sample set c

Solve 6 x 4 = 2 x + 8 for x .

6 x 4 = 2 x + 8 To isolate x on the left side, subtract 2 m from both sides . 6 x 4 2 x = 2 x + 8 2 x 4 x 4 = 8 Add 4 to both sides . 4 x 4 + 4 = 8 + 4 4 x = 12 Divide both sides by 4. 4 x 4 = 12 4 x = 3

C h e c k : 6 ( 3 ) 4 = 2 ( 3 ) + 8 Is this correct? 18 4 = 6 + 8 Is this correct? 14 = 14 Yes, this is correct .

Got questions? Get instant answers now!

Solve 6 ( 1 3 x ) + 1 = 2 x [ 3 ( x 7 ) 20 ] for x .

On left side of an equation, arrows show that six is multiplied with each term inside the parentheses, and on right side, arrows show that three is multiplied with each term inside the parentheses.

6 18 x + 1 = 2 x [ 3 x 21 20 ] 18 x + 7 = 2 x [ 3 x 41 ] 18 x + 7 = 2 x 3 x + 41 18 x + 7 = x + 41 To isolate x on the right side, add 18 x to both sides . 18 x + 7 + 18 x = x + 41 + 18 x 7 = 17 x + 41 Subtract 41 from both sides . 7 41 = 17 x + 41 41 34 = 17 x Divide both sides by 17. 34 17 = 17 x 17 2 = x Since the equation 2 = x is equivalent to the equation x = 2 , we can write the answer as x = 2. x = 2

C h e c k : 6 ( 1 3 ( 2 ) ) + 1 = 2 ( 2 ) [ 3 ( 2 7 ) 20 ] Is this correct? 6 ( 1 + 6 ) + 1 = 4 [ 3 ( 9 ) 20 ] Is this correct? 6 ( 7 ) + 1 = 4 [ 27 20 ] Is this correct? 42 + 1 = 4 [ 47 ] Is this correct? 43 = 4 + 47 Is this correct? 43 = 43 Yes, this is correct .

Got questions? Get instant answers now!

Practice set c

Solve 8 a + 5 = 3 a 5 for a .

a = 2

Got questions? Get instant answers now!

Solve 9 y + 3 ( y + 6 ) = 15 y + 21 for y .

y = 1

Got questions? Get instant answers now!

Solve 3 k + 2 [ 4 ( k 1 ) + 3 ] = 63 2 k for k .

k = 5

Got questions? Get instant answers now!

Recognizing identities and contradictions

As we noted in Section [link] , some equations are identities and some are contradictions. As the problems of Sample Set D will suggest,

    Recognizing an identity

  1. If, when solving an equation, all the variables are eliminated and a true statement results, the equation is an identity.

    Recognizing a contradiction

  1. If, when solving an equation, all the variables are eliminated and a false statement results, the equation is a contradiction.

Sample set d

Solve 9 x + 3 ( 4 3 x ) = 12 for x .

On left side of an equation, arrows show that three is multiplied with each term inside the parentheses.

9 x + 12 9 x = 12 12 = 12

The variable has been eliminated and the result is a true statement. The original equation is an identity.

Got questions? Get instant answers now!

Solve 2 ( 10 2 y ) 4 y + 1 = 18 for y .

On left side of an equation, arrows show that negative two is multiplied with each term inside the parentheses.

20 + 4 y 4 y + 1 = 18 19 = 18

The variable has been eliminated and the result is a false statement. The original equation is a contradiction.

Got questions? Get instant answers now!

Practice set d

Classify each equation as an identity or a contradiction.

6 x + 3 ( 1 2 x ) = 3

identity, 3 = 3

Got questions? Get instant answers now!

8 m + 4 ( 2 m 7 ) = 28

contradiction, 28 = 28

Got questions? Get instant answers now!

3 ( 2 x 4 ) 2 ( 3 x + 1 ) + 14 = 0

identity, 0 = 0

Got questions? Get instant answers now!

5 ( x + 6 ) + 8 = 3 [ 4 ( x + 2 ) ] 2 x

contradiction, 22 = 6

Got questions? Get instant answers now!

Exercises

For the following problems, solve each conditional equation. If the equation is not conditional, identify it as an identity or a contradiction.

2 y + 7 = 3

y = 5

Got questions? Get instant answers now!

5 x + 6 = 9

x = 3

Got questions? Get instant answers now!

10 y 3 = 23

y = 2

Got questions? Get instant answers now!

m 11 15 = 19

m = 44

Got questions? Get instant answers now!

7 x 4 + 6 = 8

x = 8

Got questions? Get instant answers now!

3 k 14 + 25 = 22

k = 14

Got questions? Get instant answers now!

3 ( x 6 ) + 5 = 25

Got questions? Get instant answers now!

16 ( y 1 ) + 11 = 85

y = 5

Got questions? Get instant answers now!

23 y 19 = 22 y + 1

y = 20

Got questions? Get instant answers now!

8 k + 7 = 2 k + 1

k = 1

Got questions? Get instant answers now!

2 ( x 7 ) = 2 x + 5

contradiction

Got questions? Get instant answers now!

4 ( 5 y + 3 ) + 5 ( 1 + 4 y ) = 0

Got questions? Get instant answers now!

3 x + 7 = 3 ( x + 2 )

x = 3

Got questions? Get instant answers now!

4 ( 4 y + 2 ) = 3 y + 2 [ 1 3 ( 1 2 y ) ]

Got questions? Get instant answers now!

5 ( 3 x 8 ) + 11 = 2 2 x + 3 ( x 4 )

x = 19 14

Got questions? Get instant answers now!

12 ( m 2 ) = 2 m + 3 m 2 m + 3 ( 5 3 m )

Got questions? Get instant answers now!

4 k ( 4 3 k ) = 3 k 2 k ( 3 6 k ) + 1

k = 3

Got questions? Get instant answers now!

3 [ 4 2 ( y + 2 ) ] = 2 y 4 [ 1 + 2 ( 1 + y ) ]

Got questions? Get instant answers now!

5 [ 2 m ( 3 m 1 ) ] = 4 m 3 m + 2 ( 5 2 m ) + 1

m = 2

Got questions? Get instant answers now!

For the following problems, solve the literal equations for the indicated variable. When directed, find the value of that variable for the given values of the other variables.

Solve I = E R for R . Find the value of R when I = 0.005 and E = 0.0035.

Got questions? Get instant answers now!

Solve P = R C for R . Find the value of R when P = 27 and C = 85.

R = 112

Got questions? Get instant answers now!

Solve z = x x ¯ s for x . Find the value of x when z = 1.96 , s = 2.5 , and x ¯ = 15.

Got questions? Get instant answers now!

Solve F = S x 2 S y 2 for S x 2 S x 2 represents a single quantity. Find the value of S x 2 when F = 2.21 and S y 2 = 3.24.

S x 2 = F · S y 2 ; S x 2 = 7.1604

Got questions? Get instant answers now!

Solve p = n R T V for R .

Got questions? Get instant answers now!

Solve x = 4 y + 7 for y .

y = x 7 4

Got questions? Get instant answers now!

Solve y = 10 x + 16 for x .

Got questions? Get instant answers now!

Solve 2 x + 5 y = 12 for y .

y = 2 x + 12 5

Got questions? Get instant answers now!

Solve 9 x + 3 y + 15 = 0 for y .

Got questions? Get instant answers now!

Solve m = 2 n h 5 for n .

n = 5 m + h 2

Got questions? Get instant answers now!

Solve t = Q + 6 P 8 for P .

Got questions? Get instant answers now!

Solve A star = + 9 j Δ for j .

j is equal to the product of star and triangle minus square over nine.

Got questions? Get instant answers now!

Exercises for review

( [link] ) Simplify ( x + 3 ) 2 ( x 2 ) 3 ( x 2 ) 4 ( x + 3 ) .

( x + 3 ) 3 ( x 2 ) 7

Got questions? Get instant answers now!

( [link] ) Find the product. ( x 7 ) ( x + 7 ) .

Got questions? Get instant answers now!

( [link] ) Find the product. ( 2 x 1 ) 2 .

4 x 2 4 x + 1

Got questions? Get instant answers now!

( [link] ) Solve the equation y 2 = 2.

Got questions? Get instant answers now!

( [link] ) Solve the equation 4 x 5 = 3.

x = 15 4

Got questions? Get instant answers now!

Questions & Answers

what is cell
Oppicial Reply
To know how bones are functions
DAUDA Reply
diagram of the heart
Victoria Reply
what are the layers of the muscles
Tongdock Reply
What is Amebae
Najibu Reply
the collection of fluids in the throat is cause by what
Emmanuel Reply
what is difference between meiosis and mitosis
Aishetu Reply
what is difference between mitosis and meiosis
Aishetu
What is Anatomy
Najibu Reply
What the difference between the Anatomy and physiology
Najibu
What is the meaning of chromoprotein
Aisha Reply
what is cartilage
Abdulkadir Reply
tough , white fibrous tissue
Henry
distinguish between anatomy and physiology
Amina Reply
Anatomy is the study of internal structure of an organism while physiology is the study of the function/relationship of the body organs working together as a system in an organism.
adeyeye
distinguish between anatomy and physiology
Erny Reply
regional anatomy is the study of the body regionally
Ismail Reply
what is the meaning of regional anatomy
Aminat Reply
epithelial tissue: it covers the Hollow organs and body cavities
Esomchi Reply
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Elementary algebra. OpenStax CNX. May 08, 2009 Download for free at http://cnx.org/content/col10614/1.3
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Elementary algebra' conversation and receive update notifications?

Ask