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This module is from Elementary Algebra by Denny Burzynski and Wade Ellis, Jr. The distinction between the principal square root of the number x and the secondary square root of the number x is made by explanation and by example. The simplification of the radical expressions that both involve and do not involve fractions is shown in many detailed examples; this is followed by an explanation of how and why radicals are eliminated from the denominator of a radical expression. Real-life applications of radical equations have been included, such as problems involving daily output, daily sales, electronic resonance frequency, and kinetic energy.Objectives of this module: be able to recognize square root equations and extraneous solutions, be able to sove square root equations.

Overview

  • Square Root Equations And Extraneous Solutions
  • Method For Solving Square Root Equations

Square root equations and extraneous solutions

Square root equation

A square root equation is an equation that contains a variable under a square root sign. The fact that x · x = ( x ) 2 = x suggests that we can solve a square root equation by squaring both sides of the equation.

Extraneous solutions

Squaring both sides of an equation can, however, introduce extraneous solutions. Consider the equation

x = 6

The solution is 6. Square both sides.

x 2 = ( 6 ) 2
x 2 = 36

This equation has two solutions, 6 and + 6. The + 6 is an extraneous solution since it does not check in the original equation: + 6 6.

Method for solving square root equations

Solving square root equations

  1. Isolate a radical. This means get a square root expression by itself on one side of the equal sign.
  2. Square both sides of the equation.
  3. Simplify the equation by combining like terms.
  4. Repeat step 1 if radicals are still present.
  5. Obtain potential solutions by solving the resulting non-square root equation.
  6. Check each potential solution by substitution into the original equation.

Sample set a

Solve each square root equation.

x = 8. The radical is isolated Square both sides . ( x ) 2 = 8 2 x = 64 Check this potential solution . C h e c k : 64 = 8 Is this correct? 8 = 8 Yes, this is correct. 64 is the solution .

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y - 3 = 4. The radical is isolated. Square both sides . y - 3 = 16 Solve this nonradical equation . y = 19 Check this potential solution . C h e c k : 19 - 3 = 16 Is this correct? 16 = 4 Is this correct? 4 = 4 Yes, this is correct. 19 is the solution .

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2 m + 3 - m - 8 = 0. Isolate either radical . 2 m + 3 = m - 8 Square both sides . 2 m + 3 = m - 8 Solve this nonradical equation . m = - 11 Check this potential solution . C h e c k : 2 ( - 11 ) + 3 - ( - 11 ) - 8 = 0 Is this correct? - 22 + 3 - - 19 = 0 Is this correct?
Since  - 19  is not a real number, the potential solution of  m = - 11  does not check . This equation has no real solution .

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4 x 5 = 6. By inspection, this equation has no real solution .
The symbol, , signifies the positive square root and not the negative square root.

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Practice set a

Solve each square root equation.

3 a + 8 2 a + 5 = 0

a = 3 is extraneous, no real solution

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m 4 = 11

no real solution

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Exercises

For the following problems, solve the square root equations.

y 4 4 = 0

y = 20

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6 m 4 = 5 m 1

m = 3

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7 a + 6 = 3 a 18

no solution

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10 a 7 2 a + 9 = 0

a = 2

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12 k 5 9 k + 10 = 0

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x 6 3 x 8 = 0

no solution

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4 a 5 7 a 20 = 0

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2 m 6 = m 2

m = 4

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3 x + 1 = 2 x 6

no solution

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2 a + 9 a 4 = 0

no solution

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At a certain electronics company, the daily output Q is related to the number of people A on the assembly line by Q = 400 + 10 A + 125 .
(a) Determine the daily output if there are 44 people on the assembly line.

(b) Determine how many people are needed on the assembly line if the daily output is to be 520.

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At a store, the daily number of sales S is approximately related to the number of employees E by S = 100 + 15 E + 6
(a) Determine the approximate number of sales if there are 19 employees.

(b) Determine the number of employees the store would need to produce 310 sales.

( a ) S = 175 ; ( b ) E = 190

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Use a calculator. The resonance frequency f in an electronic circuit containing inductance L and capacitance C in series is given by

f = 1 2 π L C

(a) Determine the resonance frequency in an electronic circuit if the inductance is 4 and the capacitance is 0.0001 . Use π = 3.14.

(b) Determine the inductance in an electric circuit if the resonance frequency is 7.12 and the capacitance is 0.0001 . Use π = 3.14.

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If two magnetic poles of strength m and m ' units are at a distance r centimeters (cm) apart, the force F of repulsion in air between them is given by

F = m m ' r 2

(a) Determine the force of repulsion if two magnetic poles of strengths 20 and 40 units are 5 cm apart in air.

(b) Determine how far apart are two magnetic poles of strengths 30 and 40 units if the force of repulsion in air between them is 0.0001 .

( a ) F = 32 ( b ) r = 8 cm

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The velocity V in feet per second of outflow of a liquid from an orifice is given by V = 8 h , where h is the height in feet of the liquid above the opening.
(a) Determine the velocity of outflow of a liquid from an orifice that is 9 feet below the top surface of a liquid ( V is in feet/sec).

(b) Determine how high a liquid is above an orifice if the velocity of outflow is 81 feet/second.

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Use a calculator. The period T in seconds of a simple pendulum of length L in feet is given by T = 2 π L 32 .

(a) Determine the period of a simple pendulum that is 2 feet long. Use π = 3.14.

(b) Determine the length in feet of a simple pendulum whose period is 10.8772 seconds. Use π = 3.14.

( a ) T = 1.57  sec  ( b ) L = 95.99  cm

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The kinetic energy K E in foot pounds of a body of mass m in slugs moving with a velocity v in feet/sec is given by

K E = 1 2 m v 2

(a) Determine the kinetic energy of a 2-slug body moving with a velocity of 4 ft/sec.

(b) Determine the velocity in feet/sec of a 4-slug body if its kinetic energy is 50 foot pounds.

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Exercises for review

( [link] ) Write x 10 y 3 ( x + 7 ) 4 x 2 y 3 ( x + 7 ) 1 so that only positive exponents appear.

x 12 ( x + 7 ) 5

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( [link] ) Classify x + 4 = x + 7 as an identity, a contradiction, or a conditional equation.

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( [link] ) Supply the missing words. In the coordinate plane, lines with slope rise and lines with slope fall.

positive; negative

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( [link] ) Simplify ( x + 3 ) 4 ( x 2 ) 6 .

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( [link] ) Simplify ( 3 + 5 ) ( 4 5 ) .

7 + 5

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Questions & Answers

Three charges q_{1}=+3\mu C, q_{2}=+6\mu C and q_{3}=+8\mu C are located at (2,0)m (0,0)m and (0,3) coordinates respectively. Find the magnitude and direction acted upon q_{2} by the two other charges.Draw the correct graphical illustration of the problem above showing the direction of all forces.
Kate Reply
To solve this problem, we need to first find the net force acting on charge q_{2}. The magnitude of the force exerted by q_{1} on q_{2} is given by F=\frac{kq_{1}q_{2}}{r^{2}} where k is the Coulomb constant, q_{1} and q_{2} are the charges of the particles, and r is the distance between them.
Muhammed
What is the direction and net electric force on q_{1}= 5µC located at (0,4)r due to charges q_{2}=7mu located at (0,0)m and q_{3}=3\mu C located at (4,0)m?
Kate Reply
what is the change in momentum of a body?
Eunice Reply
what is a capacitor?
Raymond Reply
Capacitor is a separation of opposite charges using an insulator of very small dimension between them. Capacitor is used for allowing an AC (alternating current) to pass while a DC (direct current) is blocked.
Gautam
A motor travelling at 72km/m on sighting a stop sign applying the breaks such that under constant deaccelerate in the meters of 50 metres what is the magnitude of the accelerate
Maria Reply
please solve
Sharon
8m/s²
Aishat
What is Thermodynamics
Muordit
velocity can be 72 km/h in question. 72 km/h=20 m/s, v^2=2.a.x , 20^2=2.a.50, a=4 m/s^2.
Mehmet
A boat travels due east at a speed of 40meter per seconds across a river flowing due south at 30meter per seconds. what is the resultant speed of the boat
Saheed Reply
50 m/s due south east
Someone
which has a higher temperature, 1cup of boiling water or 1teapot of boiling water which can transfer more heat 1cup of boiling water or 1 teapot of boiling water explain your . answer
Ramon Reply
I believe temperature being an intensive property does not change for any amount of boiling water whereas heat being an extensive property changes with amount/size of the system.
Someone
Scratch that
Someone
temperature for any amount of water to boil at ntp is 100⁰C (it is a state function and and intensive property) and it depends both will give same amount of heat because the surface available for heat transfer is greater in case of the kettle as well as the heat stored in it but if you talk.....
Someone
about the amount of heat stored in the system then in that case since the mass of water in the kettle is greater so more energy is required to raise the temperature b/c more molecules of water are present in the kettle
Someone
definitely of physics
Haryormhidey Reply
how many start and codon
Esrael Reply
what is field
Felix Reply
physics, biology and chemistry this is my Field
ALIYU
field is a region of space under the influence of some physical properties
Collete
what is ogarnic chemistry
WISDOM Reply
determine the slope giving that 3y+ 2x-14=0
WISDOM
Another formula for Acceleration
Belty Reply
a=v/t. a=f/m a
IHUMA
innocent
Adah
pratica A on solution of hydro chloric acid,B is a solution containing 0.5000 mole ofsodium chlorid per dm³,put A in the burret and titrate 20.00 or 25.00cm³ portion of B using melting orange as the indicator. record the deside of your burret tabulate the burret reading and calculate the average volume of acid used?
Nassze Reply
how do lnternal energy measures
Esrael
Two bodies attract each other electrically. Do they both have to be charged? Answer the same question if the bodies repel one another.
JALLAH Reply
No. According to Isac Newtons law. this two bodies maybe you and the wall beside you. Attracting depends on the mass och each body and distance between them.
Dlovan
Are you really asking if two bodies have to be charged to be influenced by Coulombs Law?
Robert
like charges repel while unlike charges atttact
Raymond
What is specific heat capacity
Destiny Reply
Specific heat capacity is a measure of the amount of energy required to raise the temperature of a substance by one degree Celsius (or Kelvin). It is measured in Joules per kilogram per degree Celsius (J/kg°C).
AI-Robot
specific heat capacity is the amount of energy needed to raise the temperature of a substance by one degree Celsius or kelvin
ROKEEB
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Source:  OpenStax, Elementary algebra. OpenStax CNX. May 08, 2009 Download for free at http://cnx.org/content/col10614/1.3
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