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Math Help - Quadratic Equations

  1. #1
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    Quadratic Equations

    Hi. Here I have questions for my assignment about solving quadratic equations using different methods. I have only ever done a few questions on quadratic equations and I dont't understand them.


    5. Solve by factorisation:

    (a) x2 + 2x + 1 = 0

    (b) x2 4 = 0

    (c) 2x2 7x 4 = 0



    6. Solve by quadratic formula to 2 decimal places:

    (a) 3x2 7x + 3 = 0

    (b) x2 + 4x + 6 = 12

    7. The diagram shows the graphs of y = x2 x, y = x + 2, y = 8 and y = -2x + 4.



    Use the graphs to find the solutions to:

    (a) x2 x = 0

    (b) x2 x = x + 2

    (c) x2 x = 8

    (d) x2 x = -2x + 4

    (e) x2 x 8 = 0

    (f) x2 + x = 4


    8. Use graphical methods to solve the following:

    (a)x2 + 3x = -2 for the range -4 < x < 2

    (b)2x2 + 5x = -2 for the range -3 < x < 0

    (c)x2 + 3x = x + 4 for the range -4 < x < 4

    As you can see there are quite a few here. So if anyone wouldn't mind could you either tell me the answes whilst helping me understand how you got the answers i.e showing workings or could you help me understand how to get answers to the questions I have listed above. Thanks
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  2. #2
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    Quote Originally Posted by Sailee316 View Post
    I have only ever done a few questions on quadratic equations and I dont't understand them.
    Then the first step is to learn the background material, so that you do "understand" quadratic equations!

    Since it is not reasonably feasible to attempt here to provide the necessary hours of course instruction, please consider using online resources instead.

    . . . . .Google results for "simple factoring"

    . . . . .Google results for "factoring quadratics"

    . . . . .Google results for "special factoring formulas"

    . . . . .Google results for "Quadratic Formula"

    For the "graphing" parts, you're just being asked to look at the pictures and copy down the values.
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  3. #3
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    I have managed to answer a few questions myself and I still am stuck on a few. The one that I really dont get is

    x2 + 4x + 6 = 12

    Solve using Quadratic formula to 2 decimal places.


    This question HAS to be solved using the Quadratic Formula. So could anyone walk me through this one question? I seem to have another few like this so if you could work through this for me I think I will be able to answer the rest myself.

    I dont think the graph one is as easy as just reading off it, or is it??? Could someone tell me the answer to the first few graph questions explaining how you got the answer and I will do the rest myself.

    Also how do you plot a quadratic for a range??. I have three of these to do

    Thanks
    Last edited by mr fantastic; April 25th 2009 at 05:17 AM.
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  4. #4
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    Quote Originally Posted by Sailee316 View Post
    Ok I will do for all future postings. I have managed to answer a few questions myself and I still am stuck on a few. The one that I really dont get is

    x2 + 4x + 6 = 12

    Solve using Quadratic formula to 2 decimal places.


    This question HAS to be solved using the Quadratic Formula. So could anyone walk me through this one question? I seem to have another few like this so if you could work through this for me I think I will be able to answer the rest myself.

    I dont think the graph one is as easy as just reading off it, or is it??? Could someone tell me the answer to the first few graph questions explaining how you got the answer and I will do the rest myself.

    Also how do you plot a quadratic for a range??. I have three of these to do

    Thanks
    Hi Sailee316,

    What's this assignment about? This is some some pretty basic stuff regarding quadratic equations that should've been covered in an instructional setting before an assignment was given. Is this a pre-test, test, or what?

    You should be familiar with the general form of the quadratic equation:

    ax^2+bx+c=0

    From this, we can generate the quadratic formula:

    x=\frac{-b \pm \sqrt{b^2-4ac}}{2a}

    Using your equation: x^2 + 4x + 6 = 12, we can convert to x^2+4x-6=0 to get it into the general form.

    From there, you know that a = 1, b = 4, and c = -6. The rest is a plug and chug operation involving simple substitution into the quadratic formula.
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  5. #5
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    Quote Originally Posted by Sailee316 View Post
    x2 + 4x + 6 = 12

    Solve using Quadratic formula to 2 decimal places.

    This question HAS to be solved using the Quadratic Formula. So could anyone walk me through this one question?
    You have been given the formula and the process, you know how to restate the above in "equals zero" form (namely, x^2 + 4x - 6 = 0), so you know the values of "a", "b", and "c" by reading them off the equation.

    Where are you stuck in the plug-n-chug process for the Quadratic Formula?

    Please show all of your steps, so we can "see" where you are needing help. Thank you!
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  6. #6
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    Hi. I have finished answering the first 5 questions so I still need to do all of the graph stuff. Im confused with these question:

    7. The diagram shows the graphs of y = x2 x, y = x + 2, y = 8 and y = -2x + 4.



    Use the graphs to find the solutions to:

    (a) x2 x = 0

    (b) x2 x = x + 2

    (c) x2 x = 8

    (d) x2 x = -2x + 4

    (e) x2 x 8 = 0

    (f) x2 + x = 4

    Im not sure how to read off this kind of graph. Help please. How exactly do I find soloutions from this graph? Please be detailed as I need to answer all these questions.

    After I have finished the question above I need to draw my own graphs right?

    8. Use graphical methods to solve the following:

    (a)x^2 + 3x = -2 for the range -4 < x < 2

    (b)2x^2 + 5x = -2 for the range -3 < x < 0

    (c)x^2 + 3x = x + 4 for the range -4 < x < 4

    Thanks
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  7. #7
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    Quote Originally Posted by Sailee316 View Post
    Hi. Here I have questions for my assignment about solving quadratic equations using different methods. I have only ever done a few questions on quadratic equations and I dont't understand them.


    5. Solve by factorisation:

    (a) x2 + 2x + 1 = 0

    (b) x2 4 = 0

    (c) 2x2 7x 4 = 0



    6. Solve by quadratic formula to 2 decimal places:

    (a) 3x2 7x + 3 = 0

    (b) x2 + 4x + 6 = 12

    7. The diagram shows the graphs of y = x2 x, y = x + 2, y = 8 and y = -2x + 4.






    Use the graphs to find the solutions to:

    (a) x2 x = 0

    (b) x2 x = x + 2

    (c) x2 x = 8

    (d) x2 x = -2x + 4

    (e) x2 x 8 = 0

    (f) x2 + x = 4


    8. Use graphical methods to solve the following:

    (a)x2 + 3x = -2 for the range -4 < x < 2

    (b)2x2 + 5x = -2 for the range -3 < x < 0

    (c)x2 + 3x = x + 4 for the range -4 < x < 4

    As you can see there are quite a few here. So if anyone wouldn't mind could you either tell me the answes whilst helping me understand how you got the answers i.e showing workings or could you help me understand how to get answers to the questions I have listed above. Thanks
    Duplicate post: http://www.mathhelpforum.com/math-he...-graphs-2.html.

    Thread closed.
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