<< 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

Ayele, K., 2003. Introductory Economics, 3rd ed., Addis Ababa.
Widad Reply
can you send the book attached ?
Ariel
?
Ariel
What is economics
Widad Reply
the study of how humans make choices under conditions of scarcity
AI-Robot
U(x,y) = (x×y)1/2 find mu of x for y
Desalegn Reply
U(x,y) = (x×y)1/2 find mu of x for y
Desalegn
what is ecnomics
Jan Reply
this is the study of how the society manages it's scarce resources
Belonwu
what is macroeconomic
John Reply
macroeconomic is the branch of economics which studies actions, scale, activities and behaviour of the aggregate economy as a whole.
husaini
etc
husaini
difference between firm and industry
husaini Reply
what's the difference between a firm and an industry
Abdul
firm is the unit which transform inputs to output where as industry contain combination of firms with similar production 😅😅
Abdulraufu
Suppose the demand function that a firm faces shifted from Qd  120 3P to Qd  90  3P and the supply function has shifted from QS  20  2P to QS 10  2P . a) Find the effect of this change on price and quantity. b) Which of the changes in demand and supply is higher?
Toofiq Reply
explain standard reason why economic is a science
innocent Reply
factors influencing supply
Petrus Reply
what is economic.
Milan Reply
scares means__________________ends resources. unlimited
Jan
economics is a science that studies human behaviour as a relationship b/w ends and scares means which have alternative uses
Jan
calculate the profit maximizing for demand and supply
Zarshad Reply
Why qualify 28 supplies
Milan
what are explicit costs
Nomsa Reply
out-of-pocket costs for a firm, for example, payments for wages and salaries, rent, or materials
AI-Robot
concepts of supply in microeconomics
David Reply
economic overview notes
Amahle Reply
identify a demand and a supply curve
Salome Reply
i don't know
Parul
there's a difference
Aryan
Demand curve shows that how supply and others conditions affect on demand of a particular thing and what percent demand increase whith increase of supply of goods
Israr
Hi Sir please how do u calculate Cross elastic demand and income elastic demand?
Abari
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