<< Chapter < Page Chapter >> Page >

Rationalize a two-term denominator

When the denominator of a fraction is a sum or difference with square roots, we use the Product of Conjugates pattern to rationalize the denominator.

( a b ) ( a + b ) ( 2 5 ) ( 2 + 5 ) a 2 b 2 2 2 ( 5 ) 2 4 5 −1

When we multiply a binomial that includes a square root by its conjugate, the product has no square roots.

Simplify: 4 4 + 2 .

Solution

.
Multiply the numerator and denominator by the conjugate of the denominator. .
Multiply the conjugates in the denominator. .
Simplify the denominator. .
Simplify the denominator. .
Remove common factors from the numerator and denominator. .
We leave the numerator in factored form to make it easier to look for common factors after we have simplified the denominator.

Got questions? Get instant answers now!
Got questions? Get instant answers now!

Simplify: 2 2 + 3 .

2 ( 2 3 ) 1

Got questions? Get instant answers now!

Simplify: 5 5 + 3 .

5 ( 5 3 ) 22

Got questions? Get instant answers now!

Simplify: 5 2 3 .

Solution

.
Multiply the numerator and denominator by the conjugate of the denominator. .
Multiply the conjugates in the denominator. .
Simplify the denominator. .
Simplify the denominator. .
Simplify. .

Got questions? Get instant answers now!
Got questions? Get instant answers now!

Simplify: 3 1 5 .

3 ( 1 + 5 ) 4

Got questions? Get instant answers now!

Simplify: 2 4 6 .

4 + 6 5

Got questions? Get instant answers now!

Simplify: 3 u 6 .

Solution

.
Multiply the numerator and denominator by the conjugate of the denominator. .
Multiply the conjugates in the denominator. .
Simplify the denominator. .

Got questions? Get instant answers now!
Got questions? Get instant answers now!

Simplify: 5 x + 2 .

5 ( x 2 ) x 2

Got questions? Get instant answers now!

Simplify: 10 y 3 .

10 ( y + 3 ) y 3

Got questions? Get instant answers now!

Simplify: x + 7 x 7 .

Solution

.
Multiply the numerator and denominator by the conjugate of the denominator. .
Multiply the conjugates in the denominator. .
Simplify the denominator. .
We do not square the numerator. In factored form, we can see there are no common factors to remove from the numerator and denominator.

Got questions? Get instant answers now!
Got questions? Get instant answers now!

Simplify: p + 2 p 2 .

( p + 2 ) p 2 2

Got questions? Get instant answers now!

Simplify: q 10 q + 10 .

( q 10 ) q 10 2

Got questions? Get instant answers now!

Access this online resource for additional instruction and practice with dividing and rationalizing.

Key concepts

  • Quotient Property of Square Roots
    • If a , b are non-negative real numbers and b 0 , then
      a b = a b and a b = a b
  • Simplified Square Roots
    A square root is considered simplified if there are
    • no perfect square factors in the radicand
    • no fractions in the radicand
    • no square roots in the denominator of a fraction

Practice makes perfect

Divide Square Roots

In the following exercises, simplify.

8 x 6 2 x 2 200 m 5 98 m

2 x 2 10 m 2 7

Got questions? Get instant answers now!

10 y 3 5 y 108 n 7 243 n 3

Got questions? Get instant answers now!

108 p 5 q 2 34 p 3 q 6

6 p q 2

Got questions? Get instant answers now!

320 m n 5 45 m 7 n 3

8 n 3 m 3

Got questions? Get instant answers now!

Rationalize a One-Term Denominator

In the following exercises, simplify and rationalize the denominator.

Rationalize a Two-Term Denominator

In the following exercises, simplify by rationalizing the denominator.

3 3 + 11 8 1 5

3 ( 3 11 ) −2 −2 ( 1 + 5 )

Got questions? Get instant answers now!

4 4 + 7 7 2 6

Got questions? Get instant answers now!

5 5 + 6 6 3 7

5 ( 5 6 ) 19 3 ( 3 + 7 )

Got questions? Get instant answers now!

6 6 + 5 5 4 11

Got questions? Get instant answers now!

3 m 5

3 ( m + 5 ) m 5

Got questions? Get instant answers now!

2 x 6

2 ( x + 3 ) x 6

Got questions? Get instant answers now!

r + 5 r 5

( r + 5 ) r 5 2

Got questions? Get instant answers now!

150 x 2 y 6 6 x 4 y 2

5 y 2 x

Got questions? Get instant answers now!

3 5 + 5

3 ( 5 5 ) 20

Got questions? Get instant answers now!

2 x 3

2 ( x + 3 ) x 3

Got questions? Get instant answers now!

x + 8 x 8

( x + 2 2 ) x 8 2

Got questions? Get instant answers now!

Everyday math

A supply kit is dropped from an airplane flying at an altitude of 250 feet. Simplify 250 16 to determine how many seconds it takes for the supply kit to reach the ground.

5 10 4 seconds

Got questions? Get instant answers now!

A flare is dropped into the ocean from an airplane flying at an altitude of 1,200 feet. Simplify 1200 16 to determine how many seconds it takes for the flare to reach the ocean.

Got questions? Get instant answers now!

Writing exercises


Simplify 27 3 and explain all your steps.
Simplify 27 5 and explain all your steps.
Why are the two methods of simplifying square roots different?

Answers will vary.

Got questions? Get instant answers now!
  1. Approximate 1 2 by dividing 1 1.414 using long division without a calculator.
  2. Rationalizing the denominator of 1 2 gives 2 2 . Approximate 2 2 by dividing 1.414 2 using long division without a calculator.
  3. Do you agree that rationalizing the denominator makes calculations easier? Why or why not?
Got questions? Get instant answers now!

Self check

After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

This table has four columns and four rows. The columns are labeled, “I can…,” “confidently.,” “with some help.,” and “no – I don’t get it!” The rows under the column “I can…” read, “divide square roots,” “rationalize a one term denominator.,” and “rationalize a two term denominator.” All the other rows under the columns are empty.

After looking at the checklist, do you think you are well-prepared for the next section? Why or why not?

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
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
Practice Key Terms 1

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. Jan 18, 2017 Download for free at http://cnx.org/content/col12116/1.2
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