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By the end of this section, you will be able to:
  • Multiply rational expressions
  • Divide rational expressions

Before you get started, take this readiness quiz.

If you miss a problem, go back to the section listed and review the material.

  1. Multiply: 14 15 · 6 35 .
    If you missed this problem, review [link] .
  2. Divide: 14 15 ÷ 6 35 .
    If you missed this problem, review [link] .
  3. Factor completely: 2 x 2 98 .
    If you missed this problem, review [link] .
  4. Factor completely: 10 n 3 + 10 .
    If you missed this problem, review [link] .
  5. Factor completely: 10 p 2 25 p q 15 q 2 .
    If you missed this problem, review [link] .

Multiply rational expressions

To multiply rational expressions, we do just what we did with numerical fractions. We multiply the numerators and multiply the denominators. Then, if there are any common factors, we remove them to simplify the result.

Multiplication of rational expressions

If p , q , r , s are polynomials where q 0 and s 0 , then

p q · r s = p r q s

To multiply rational expressions, multiply the numerators and multiply the denominators.

We’ll do the first example with numerical fractions to remind us of how we multiplied fractions without variables.

Multiply: 10 28 · 8 15 .

Solution

.
Multiply the numerators and denominators. .
Look for common factors, and then remove them. .
Simplify. .

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Mulitply: 6 10 · 15 12 .

3 4

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Mulitply: 20 15 · 6 8 .

1

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Remember, throughout this chapter, we will assume that all numerical values that would make the denominator be zero are excluded. We will not write the restrictions for each rational expression, but keep in mind that the denominator can never be zero. So in this next example, x 0 and y 0 .

Mulitply: 2 x 3 y 2 · 6 x y 3 x 2 y .

Solution

.
Multiply. .
Factor the numerator and denominator completely, and then remove common factors. .
Simplify. .

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Mulitply: 3 p q q 2 · 5 p 2 q 6 p q .

5 p 2 q

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Mulitply: 6 x 3 y 7 x 2 · 2 x y 3 x 2 y .

12 y 3 7

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How to multiply rational expressions

Mulitply: 2 x x 2 + x + 12 · x 2 9 6 x 2 .

Solution

The above image has three columns and three rows to show how to multiply rational expressions. Step one is to factor each numerator and denominator completely. Factor x squared minus 9 and x squared plus x plus 12. The rational equation is 2x divided by x squared plus x plus 12 times x squared minus 9 divided by 6x squared, then to 2x divided by x minus 3 times x minus 4 times x minus 3 times x plus 3 divided by 6x squared. Step 2 is to multiply the numerators and denominators. It is helpful to multiply the monomials first. Multiply 2x times x minus 3 times x plus 3 divided by 6x squared times x minus 3 times x minus 4. Step 3 is to divide out the common factors, canceling out 2, x, and x minus 3 in the numerator and 2, x and x minus 3 in the denominator. Leave the denominator in factored form to get x plus 3 divided by 3x times x minus 4.
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Mulitply: 5 x x 2 + 5 x + 6 · x 2 4 10 x .

x 2 2 ( x + 3 )

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Mulitply: 9 x 2 x 2 + 11 x + 30 · x 2 36 3 x 2 .

3 ( x 6 ) x + 5

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Multiply a rational expression.

  1. Factor each numerator and denominator completely.
  2. Multiply the numerators and denominators.
  3. Simplify by dividing out common factors.

Multiply: n 2 7 n n 2 + 2 n + 1 · n + 1 2 n .

Solution

n 2 7 n n 2 + 2 n + 1 · n + 1 2 n Factor each numerator and denominator. n ( n 7 ) ( n + 1 ) ( n + 1 ) · n + 1 2 n Multiply the numerators and the denominators. n ( n 7 ) ( n + 1 ) ( n + 1 ) ( n + 1 ) 2 n Remove common factors. n ( n 7 ) ( n + 1 ) ( n + 1 ) ( n + 1 ) 2 n Simplify. n 7 2 ( n + 1 )

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Multiply: x 2 25 x 2 3 x 10 · x + 2 x .

x + 5 x

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Multiply: x 2 4 x x 2 + 5 x + 6 · x + 2 x .

x 4 x + 3

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Multiply: 16 4 x 2 x 12 · x 2 5 x 6 x 2 16 .

Solution

16 4 x 2 x 12 · x 2 5 x 6 x 2 16 Factor each numerator and denominator. 4 ( 4 x ) 2 ( x 6 ) · ( x 6 ) ( x + 1 ) ( x 4 ) ( x + 4 ) Multiply the numerators and the denominators. 4 ( 4 x ) ( x 6 ) ( x + 1 ) 2 ( x 6 ) ( x 4 ) ( x + 4 ) Remove common factors. ( −1 ) 2 · 2 ( 4 x ) ( x 6 ) ( x + 1 ) 2 ( x 6 ) ( x 4 ) ( x + 4 ) Simplify. 2 ( x + 1 ) ( x + 4 )

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Multiply: 12 x 6 x 2 x 2 + 8 x · x 2 + 11 x + 24 x 2 4 .

6 ( x + 3 ) x + 2

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Multiply: 9 v 3 v 2 9 v + 36 · v 2 + 7 v + 12 v 2 9 .

v 3

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Multiply: 2 x 6 x 2 8 x + 15 · x 2 25 2 x + 10 .

Solution

.
Factor each numerator and denominator. .
Multiply the numerators and denominators. .
Remove common factors. .
Simplify. .

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Multiply: 3 a 21 a 2 9 a + 14 · a 2 4 3 a + 6 .

1

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Multiply: b 2 b b 2 + 9 b 10 · b 2 100 b 2 10 b .

1

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Divide rational expressions

To divide rational expressions we multiply the first fraction by the reciprocal of the second, just like we did for numerical fractions.

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