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Solving a quadratic equation using grouping

Use grouping to factor and solve the quadratic equation: 4 x 2 + 15 x + 9 = 0.

First, multiply a c : 4 ( 9 ) = 36. Then list the factors of 36.

1 36 2 18 3 12 4 9 6 6

The only pair of factors that sums to 15 is 3 + 12. Rewrite the equation replacing the b term, 15 x , with two terms using 3 and 12 as coefficients of x . Factor the first two terms, and then factor the last two terms.

4 x 2 + 3 x + 12 x + 9 = 0 x ( 4 x + 3 ) + 3 ( 4 x + 3 ) = 0 ( 4 x + 3 ) ( x + 3 ) = 0

Solve using the zero-product property.

( 4 x + 3 ) ( x + 3 ) = 0 ( 4 x + 3 ) = 0 x = 3 4 ( x + 3 ) = 0 x = 3

The solutions are 3 4 , and −3. See [link] .

Coordinate plane with the x-axis ranging from negative 6 to 2 with every other tick mark labeled and the y-axis ranging from negative 6 to 2 with each tick mark numbered. The equation: four x squared plus fifteen x plus nine is graphed with its x-intercepts: (-3/4,0) and (-3,0) plotted as well.
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Solve using factoring by grouping: 12 x 2 + 11 x + 2 = 0.

( 3 x + 2 ) ( 4 x + 1 ) = 0 , x = 2 3 , x = 1 4

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Solving a polynomial of higher degree by factoring

Solve the equation by factoring: −3 x 3 5 x 2 2 x = 0.

This equation does not look like a quadratic, as the highest power is 3, not 2. Recall that the first thing we want to do when solving any equation is to factor out the GCF, if one exists. And it does here. We can factor out x from all of the terms and then proceed with grouping.

−3 x 3 5 x 2 2 x = 0 x ( 3 x 2 + 5 x + 2 ) = 0

Use grouping on the expression in parentheses.

x ( 3 x 2 + 3 x + 2 x + 2 ) = 0 x [ 3 x ( x + 1 ) + 2 ( x + 1 ) ] = 0 x ( 3 x + 2 ) ( x + 1 ) = 0

Now, we use the zero-product property. Notice that we have three factors.

x = 0 x = 0 3 x + 2 = 0 x = 2 3 x + 1 = 0 x = −1

The solutions are 0 , 2 3 , and −1.

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Solve by factoring: x 3 + 11 x 2 + 10 x = 0.

x = 0 , x = −10 , x = −1

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Using the square root property

When there is no linear term in the equation, another method of solving a quadratic equation is by using the square root property    , in which we isolate the x 2 term and take the square root of the number on the other side of the equals sign. Keep in mind that sometimes we may have to manipulate the equation to isolate the x 2 term so that the square root property can be used.

The square root property

With the x 2 term isolated, the square root property states that:

if x 2 = k , then x = ± k

where k is a nonzero real number.

Given a quadratic equation with an x 2 term but no x term, use the square root property to solve it.

  1. Isolate the x 2 term on one side of the equal sign.
  2. Take the square root of both sides of the equation, putting a ± sign before the expression on the side opposite the squared term.
  3. Simplify the numbers on the side with the ± sign.

Solving a simple quadratic equation using the square root property

Solve the quadratic using the square root property: x 2 = 8.

Take the square root of both sides, and then simplify the radical. Remember to use a ± sign before the radical symbol.

x 2 = 8 x = ± 8 = ± 2 2

The solutions are 2 2 , −2 2 .

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Solving a quadratic equation using the square root property

Solve the quadratic equation: 4 x 2 + 1 = 7.

First, isolate the x 2 term. Then take the square root of both sides.

4 x 2 + 1 = 7 4 x 2 = 6 x 2 = 6 4 x = ± 6 2

The solutions are 6 2 , and 6 2 .

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Solve the quadratic equation using the square root property: 3 ( x 4 ) 2 = 15.

x = 4 ± 5

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Completing the square

Not all quadratic equations can be factored or can be solved in their original form using the square root property. In these cases, we may use a method for solving a quadratic equation    known as completing the square    . Using this method, we add or subtract terms to both sides of the equation until we have a perfect square trinomial on one side of the equal sign. We then apply the square root property. To complete the square, the leading coefficient, a , must equal 1. If it does not, then divide the entire equation by a . Then, we can use the following procedures to solve a quadratic equation by completing the square.

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, Algebra and trigonometry. OpenStax CNX. Nov 14, 2016 Download for free at https://legacy.cnx.org/content/col11758/1.6
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