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Thread: quadratic equation from amazing lil boy

  1. #1
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    quadratic equation from amazing lil boy

    hi there i want help with this quadratic equation.. im quiet young.. so try to explain it step by step so i can understand

    y= 2x3+3x+19

    p.s. the first 3 is squared

    can someone identify a b and c value?? Thanks very much.. try fully explain it to me so i can do it next time by myself.. thanks
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    Bar0n janvdl's Avatar
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    Quote Originally Posted by pitt View Post
    hi there i want help with this quadratic equation.. im quiet young.. so try to explain it step by step so i can understand

    y= 2x3+3x+19

    p.s. the first 3 is squared

    can someone identify a b and c value?? Thanks very much.. try fully explain it to me so i can do it next time by myself.. thanks
    Did you mean $\displaystyle 3x^2 + 3x + 19$ ?

    A quadratic equation is in the format: $\displaystyle ax^2 + bx + c$

    Do you want the equation solved?

    $\displaystyle 0 = 3x^2 + 3x + (19 - y)$ [That part in brackets is your c-value]

    We know that $\displaystyle x = \frac{ -b +- \sqrt{b^2 - 4ac}}{2a}$

    So simply set the values into the equation:

    $\displaystyle x = \frac{ -(3) +- \sqrt{(3)^2 - 4(3)(19 - y)}}{2(3)}$

    $\displaystyle x = \frac{ -(3) +- \sqrt{12y - 219}}{6}$

    It seems that for this equation to be true, $\displaystyle y > 18,25$
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  3. #3
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    i didnt understand anything :S
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  4. #4
    Bar0n janvdl's Avatar
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    Quote Originally Posted by pitt View Post
    i didnt understand anything :S
    Be more specific?
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    Where did u get the 4 from?? and why do you put numbers 3 on brackets??
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    Bar0n janvdl's Avatar
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    Quote Originally Posted by pitt View Post


    Where did u get the 4 from?? and why do you put numbers 3 on brackets??
    Have you heard about the quadratic formula yet?
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    Quote Originally Posted by janvdl View Post
    Have you heard about the quadratic formula yet?
    ye but i cant remember what the formula is.. do you mind if you explain it to me?? thanks
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    Bar0n janvdl's Avatar
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    Quote Originally Posted by pitt View Post
    ye but i cant remember what the formula is.. do you mind if you explain it to me?? thanks
    If you have the formula: $\displaystyle 2x^2 + 3x + 4$, then the 2 is your a value, the 3 is your b value, and the 4 is your c value.

    Like i said before: quadratic equations are in the format: $\displaystyle ax^2 + bx + c$

    I'm sure you understand that.

    The quadratic formula: $\displaystyle x = \frac{ -b +- \sqrt{b^2 - 4ac}}{2a}$

    Thats how the formula looks, and you have to learn that format.

    Let's say we want to solve that equation at the top that i used to explain.

    Then wherever there is an a, we substitute it with 2.
    Wherever there is a b, we substitute it with 3.
    Wherever there is a c, we substitute it with 4.

    Do you understand?
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    Bar0n janvdl's Avatar
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    I'm just letting you know that I have to leave now. Sorry.

    Soroban is around, he'll probably continue where I left off.

    Have a good night.
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  10. #10
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    ye thanks very much.. i understood almost evertyhing just want to know how did you get 12 and 219... can anyone explain it?? and then how did he get 18??

    so

    a value is= 3

    b= 4

    c = 19

    am i right??
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    oh ye one more thing.. you said wherever theres an a, i should substitute it with a 2.. why if you look at number 2 theres a bracket after it with number 3.. but the equation shows 2a.. why did u put 2(3) instead of 2(2)
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    Wink Solving Quadratic Equations

    Quote Originally Posted by pitt View Post
    hi there i want help with this quadratic equation.. im quiet young.. so try to explain it step by step so i can understand

    y= 2x3+3x+19

    p.s. the first 3 is squared

    can someone identify a b and c value?? Thanks very much.. try fully explain it to me so i can do it next time by myself.. thanks

    To be a quadratic equation, it needs x^2 in it, where the power symbol ^ is used to mean that x is to the power 2.

    You can learn a lot by reading some worked out examples as well as entering your own at webgraphing.com:

    Free Online Quadratic Equation Solver: Solve by Quadratic Formula

    It will give you step by step walk through on any quadratic equation. To start you might just click the button for solving a random equation, just to see how it looks. Then enter your own and read the worked-out solution.
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by janvdl View Post
    If you have the formula: $\displaystyle 2x^2 + 3x + 4$, then the 2 is your a value, the 3 is your b value, and the 4 is your c value.

    Like i said before: quadratic equations are in the format: $\displaystyle ax^2 + bx + c$

    I'm sure you understand that.

    The quadratic formula: $\displaystyle x = \frac{ -b +- \sqrt{b^2 - 4ac}}{2a}$

    Thats how the formula looks, and you have to learn that format.

    Let's say we want to solve that equation at the top that i used to explain.

    Then wherever there is an a, we substitute it with 2.
    Wherever there is a b, we substitute it with 3.
    Wherever there is a c, we substitute it with 4.

    Do you understand?
    use \pm to get $\displaystyle \pm$
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  14. #14
    Bar0n janvdl's Avatar
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    Quote Originally Posted by pitt View Post


    oh ye one more thing.. you said wherever theres an a, i should substitute it with a 2.. why if you look at number 2 theres a bracket after it with number 3.. but the equation shows 2a.. why did u put 2(3) instead of 2(2)
    Oh yes, it should be 2(2). Thanks for the spot.

    Try to spend a little time on it yourself to see how i got the values there. I simplified everything under the root.
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    Quote Originally Posted by pitt View Post
    hi there i want help with this quadratic equation.. im quiet young.. so try to explain it step by step so i can understand

    y= 2x3+3x+19

    p.s. the first 3 is squared

    can someone identify a b and c value?? Thanks very much.. try fully explain it to me so i can do it next time by myself.. thanks
    See this

    RonL
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