<< Chapter < Page Chapter >> Page >
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 .

Got questions? Get instant answers now!

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 .

Got questions? Get instant answers now!

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 .

Got questions? Get instant answers now!

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.

Got questions? Get instant answers now!

Practice set a

Solve each square root equation.

3 a + 8 2 a + 5 = 0

a = 3 is extraneous, no real solution

Got questions? Get instant answers now!

m 4 = 11

no real solution

Got questions? Get instant answers now!

Exercises

For the following problems, solve the square root equations.

y 4 4 = 0

y = 20

Got questions? Get instant answers now!

6 m 4 = 5 m 1

m = 3

Got questions? Get instant answers now!

7 a + 6 = 3 a 18

no solution

Got questions? Get instant answers now!

10 a 7 2 a + 9 = 0

a = 2

Got questions? Get instant answers now!

12 k 5 9 k + 10 = 0

Got questions? Get instant answers now!

x 6 3 x 8 = 0

no solution

Got questions? Get instant answers now!

4 a 5 7 a 20 = 0

Got questions? Get instant answers now!

2 m 6 = m 2

m = 4

Got questions? Get instant answers now!

3 x + 1 = 2 x 6

no solution

Got questions? Get instant answers now!

2 a + 9 a 4 = 0

no solution

Got questions? Get instant answers now!

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.

Got questions? Get instant answers now!

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

Got questions? Get instant answers now!

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.

Got questions? Get instant answers now!

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

Got questions? Get instant answers now!

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.

Got questions? Get instant answers now!

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

Got questions? Get instant answers now!

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.

Got questions? Get instant answers now!

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

Got questions? Get instant answers now!

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

Got questions? Get instant answers now!

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

positive; negative

Got questions? Get instant answers now!

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

Got questions? Get instant answers now!

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

7 + 5

Got questions? Get instant answers now!

Questions & Answers

how does the planets on our solar system orbit
cheten Reply
how many Messier objects are there in space
satish Reply
did you g8ve certificate
Richard Reply
what are astronomy
Issan Reply
Astronomy (from Ancient Greek ἀστρονομία (astronomía) 'science that studies the laws of the stars') is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution.
Rafael
vjuvu
Elgoog
what is big bang theory?
Rosemary
what type of activity astronomer do?
Rosemary
No
Richard
the big bang theory is a theory which states that all matter was compressed together in one place the matter got so unstable it exploded releasing All its contents in the form of hydrogen
Roaul
I want to be an astronomer. That's my dream
Astrit
Who named the the whole galaxy?
Shola Reply
solar Univers
GPOWER
what is space
Richard
what is the dark matter
Richard
what are the factors upon which the atmosphere is stratified
Nicholas Reply
is the big bang the sun
Folakemi Reply
no
Sokak
bigbang is the beginning of the universe
Sokak
but thats just a theory
Sokak
nothing will happen, don't worry brother.
Vansh
what does comet means
GANGAIN Reply
these are Rocky substances between mars and jupiter
GANGAIN
Comets are cosmic snowballs of frozen gases , rock and dust that orbit the sun. They are mostly found between the orbits of Venus and Mercury.
Aarya
hllo
John
hi
John
qt rrt
John
r u there
John
hey can anyone guide me abt international astronomy olympiad
sahil
how can we learn right and true ?
Govinda Reply
why the moon is always appear in an elliptical shape
Gatjuol Reply
Because when astroid hit the Earth then a piece of elliptical shape of the earth was separated which is now called moon.
Hemen
what's see level?
lidiya Reply
Did you mean eye sight or sea level
Minal
oh sorry it's sea level
lidiya
according to the theory of astronomers why the moon is always appear in an elliptical orbit?
Gatjuol
hi !!! I am new in astronomy.... I have so many questions in mind .... all of scientists of the word they just give opinion only. but they never think true or false ... i respect all of them... I believes whole universe depending on true ...থিউরি
Govinda
hello
Jackson
hi
Elyana
we're all stars and galaxies a part of sun. how can science prove thx with respect old ancient times picture or books..or anything with respect to present time .but we r a part of that universe
w astronomy and cosmology!
Michele
another theory of universe except big ban
Albash Reply
how was universe born
Asmit Reply
there many theory to born universe but what is the reality of big bang theory to born universe
Asmit
what is the exact value of π?
Nagalakshmi
by big bang
universal
there are many theories regarding this it's on you believe any theory that you think is true ex. eternal inflation theory, oscillation model theory, multiple universe theory the big bang theory etc.
Aarya
I think after Big Bang!
Michele
from where on earth could u observe all the stars during the during the course of an year
Karuna Reply
I think it couldn't possible on earth
Nagalakshmi
in this time i don't Know
Michele
is that so. the question was in the end of this chapter
Karuna
in theory, you could see them all from the equator (though over the course of a year, not at pne time). stars are measured in "declination", which is how far N or S of the equator (90* to -90*). Polaris is the North star, and is ALMOST 90* (+89*). So it would just barely creep over the horizon.
Christopher
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