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This module is from Elementary Algebra</link>by Denny Burzynski and Wade Ellis, Jr. Methods of solving quadratic equations as well as the logic underlying each method are discussed. Factoring, extraction of roots, completing the square, and the quadratic formula are carefully developed. The zero-factor property of real numbers is reintroduced. The chapter also includes graphs of quadratic equations based on the standard parabola, y = x^2, and applied problems from the areas of manufacturing, population, physics, geometry, mathematics (numbers and volumes), and astronomy, which are solved using the five-step method.Objectives of this module: be able to construct the graph of a parabola.

Overview

  • Parabolas
  • Constructing Graphs of Parabolas

Parabolas

We will now study the graphs of quadratic equations in two variables with general form y = a x 2 + b x + c , a 0 , a , b , c are real numbers

Parabola

All such graphs have a similar shape. The graph of a quadratic equation of this type Parabola is called a parabola and it will assume one of the following shapes.

Two parabolas, one opening upward and one opening downward. The lowest point of the parabola opening upward and the highest point of the parabola opening downward are each labeled as 'Vertex.'

Vertex

The high point or low point of a parabola is called the vertex of the parabola.

Constructing graphs of parabolas

We will construct the graph of a parabola by choosing several x -values, computing to find the corresponding y -values, plotting these ordered pairs, then drawing a smooth curve through them.

Sample set a

Graph y = x 2 .    Construct a table to exhibit several ordered pairs.

x y = x 2
0 0
1 1
2 4
3 9
1 1
2 4
3 9


A graph of a parabola passing through five points with coordinates negative two, four; negative one, one; zero, zero; one, one; and two, four.

This is the most basic parabola. Although other parabolas may be wider, narrower, moved up or down, moved to the left or right, or inverted, they will all have this same basic shape. We will need to plot as many ordered pairs as necessary to ensure this basic shape.

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Graph y = x 2 2 .     Construct a table of ordered pairs.

x y = x 2 2
0 2
1 1
2 2
3 7
1 1
2 2
3 7


A graph of a parabola passing through five points with coordinates negative two, two; negative one , negative one; zero, negative two, one, negative one; and two, two.

Notice that the graph of y = x 2 2 is precisely the graph of y = x 2 but translated 2 units down. Compare the equations y = x 2 and y = x 2 2 . Do you see what causes the 2 unit downward translation?

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Practice set a

Use the idea suggested in Sample Set A to sketch (quickly and perhaps not perfectly accurately) the graphs of

y = x 2 + 1 and y = x 2 3

An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.    An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.

A graph of a quadratic equation y equals x square plus one passing through five points with coordinates negative two, five; negative one, two; zero, one; one, two; and two, five.    A graph of a quadratic equation y equals x square minus three passing through five points with coordinates negative two, one; negative one, negative two; zero, negative three; one, negative two; and two, one.

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Sample set b

Graph y = ( x + 2 ) 2 .

Do we expect the graph to be similar to the graph of y = x 2 ? Make a table of ordered pairs.

x y
0 4
1 9
1 1
2 0
3 1
4 4


A graph of a parabola passing through five points with coordinates negative four, four; negative three, one; negative two, zero;negative one, one; and zero, four.

Notice that the graph of y = ( x + 2 ) 2 is precisely the graph of y = x 2 but translated 2 units to the left. The +2 inside the parentheses moves y = x 2 two units to the left. A negative value inside the parentheses makes a move to the right.

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Practice set b

Use the idea suggested in Sample Set B to sketch the graphs of

y = ( x 3 ) 2 and y = ( x + 1 ) 2

An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.

A graph of a quadratic equation y equals x minus three the whole square passing through five points  with the coordinates one, four; two, one; three, zero; four, one; and five, four.    A graph of a quadratic equation y equals x plus one the whole square passing through five points  with the coordinates negative three, four; negative two, one; negative one, zero; zero, one; and one, four.

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Graph y = ( x 2 ) 2 + 1

An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.

A graph of a quadratic equation y equals x square minus three passing through five points with the coordinates zero, five; one, two; two, one; three, two; and four, five.

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Exercises

For the following problems, graph the quadratic equations.

y = ( x 1 ) 2

An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.

y = ( x 1 ) 2

A graph of a parabola passing through five points with coordinates negative one, four; zero, one; one, zero, two, one; and three, four.

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y = ( x + 3 ) 2

An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.

y = ( x + 3 ) 2

A graph of a parabola passing through five points with coordinates negative five, four; negative four, one; negative three,zero; negative two, one; and negative one, four.

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y = x 2 3

An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.

y = x 2 3

A graph of a parabola passing through seven points with coordinates negative three, six; negative two, one; negative one, negative two; zero, negative three; one, negative two; two, one; and three, six.

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y = x 2 1 2

An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.

y = x 2 1 2

A graph of a parabola passing through five points with coordinates negative two, seven over two; negative one, one over two; zero, negative one over two; one, one over two; and two, seven over two.

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y = x 2 + 1 (Compare with problem 2.)

An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.

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y = x 2 1 (Compare with problem 1.)

An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.

y = x 2 1

A graph of a parabola passing through five points with coordinates negative two, negative five; negative one, negative two; zero, negative one, one, negative two; and two, negative five.

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y = ( x + 3 ) 2 + 2

An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.

y = ( x + 3 ) 2 + 2

A graph of a parabola passing through five points with coordinates negative five, six; negative four, three; negative three, two; negative two, three; and negative one, six.

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y = ( x + 3 ) 2

An xy coordinate plane with gridlines, labeled negative five and five with increments of one units on both axes.

y = ( x + 3 ) 2

A graph of a parabola passing through five points with coordinates negative five, negative four; negative four, negative one; negative three, zero; negative two, negative one; and negative one, negative four.

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For the following problems, try to guess the quadratic equation that corresponds to the given graph.

Exercises for review

( [link] ) Simplify and write ( x 4 y 5 ) 3 ( x 6 y 4 ) 2 so that only positive exponents appear.

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( [link] ) Factor y 2 y 42.

( y + 6 ) ( y 7 )

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( [link] ) Find the sum: 2 a 3 + 3 a + 3 + 18 a 2 9 .

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( [link] ) Simplify 2 4 + 5 .

8 2 5 11

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( [link] ) Four is added to an integer and that sum is doubled. When this result is multiplied by the original integer, the product is 6. Find the integer.

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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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