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Math Help - Need some major help!!! i'm about to go nuts~

  1. #16
    Junior Member mcdanielnc89's Avatar
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    Wow, I can't believe I actually got that all right, excluding the y-coordinate. I don't know why I didn't search for algebra forums before, LOL...


    So, The minimum value will be -6.07


    Now, this might be a dumb question, but how do I find the two x-coordinates?
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  2. #17
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by mcdanielnc89 View Post
    Wow, I can't believe I actually got that all right, excluding the y-coordinate. I don't know why I didn't search for algebra forums before, LOL...


    So, The minimum value will be -6.07


    Now, this might be a dumb question, but how do I find the two x-coordinates?
    Do you mean x intercepts?

    You need to set the quadratic equation equal to zero.

    5.71x^2 - 3.135x-5.64=0

    You will need to use the quadratic formula.

    In case you forgot it, the quadratic formula is x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}

    --Chris
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  3. #18
    Junior Member mcdanielnc89's Avatar
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    Quote Originally Posted by Chris L T521 View Post
    Do you mean x intercepts?

    You need to set the quadratic equation equal to zero.

    5.71x^2 - 3.135x-5.64=0

    You will need to use the quadratic formula.

    In case you forgot it, the quadratic formula is x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}

    --Chris
    Thank you.. I will see if i get it right in a few minutes. Be back with an answer!! hehe.. BRB.
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  4. #19
    Junior Member mcdanielnc89's Avatar
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    Okay well I'm back.. How's these two answers?


    14.135 and -7.865




    I will return in the mornign and pick up from here. I'm so tired, I've been working on this since 11 am CST...
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  5. #20
    Junior Member mcdanielnc89's Avatar
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    Quote Originally Posted by mcdanielnc89 View Post
    Okay well I'm back.. How's these two answers?


    14.135 and -7.865




    I will return in the mornign and pick up from here. I'm so tired, I've been working on this since 11 am CST...
    Well, I'm back.. so are these anywhere near right?
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  6. #21
    Junior Member mcdanielnc89's Avatar
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    bump`
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  7. #22
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by Chris L T521 View Post
    Do you mean x intercepts?

    You need to set the quadratic equation equal to zero.

    5.71x^2 - 3.135x-5.64=0

    You will need to use the quadratic formula.

    In case you forgot it, the quadratic formula is x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}

    --Chris
    Quote Originally Posted by mcdanielnc89 View Post
    Okay well I'm back.. How's these two answers?


    14.135 and -7.865




    I will return in the mornign and pick up from here. I'm so tired, I've been working on this since 11 am CST...
    How did you get these values?

    Solving 5.71x^2-3.135x-5.64=0, we get x=\frac{3.135\pm\sqrt{138.646}}{11.42}\implies x\approx 1.306 and x\approx-.757.

    Does this make sense?

    --Chris
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  8. #23
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    Quote Originally Posted by mcdanielnc89 View Post
    Okay well I'm back.. How's these two answers?
    14.135 and -7.865
    no, they are not correct.

    5.71x^2 - 3.135x - 5.64 = 0

    learn to use the store capability of the calculator. the "store" button is just above the ON button labeled [STO->] ... type the number first, hit the store button (you get the arrow), then type in the letter of the alphabet where you want it. A, B, and C are good choices since they represent the values in the quadratic formula.

    5.71 -> A
    -3.135 -> B
    -5.64 -> C

    now type in on the home screen ...

    (-B + \sqrt(B^2 - 4AC))/(2A)
    for one the first root.

    {note that the negative sign in front of B is the small negative sign, whereas the minus sign between B^2 and 4AC is the subtraction sign}

    press [2nd][ENTER] to recall the last expression, change the + to a - ...

    (-B - \sqrt(B^2 - 4AC))/(2A)
    for the second root.

    you should get 1.305586355 and -.7565495776
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  9. #24
    Junior Member mcdanielnc89's Avatar
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    Quote Originally Posted by Chris L T521 View Post
    How did you get these values?

    Solving 5.71x^2-3.135x-5.64=0, we get x=\frac{3.135\pm\sqrt{138.646}}{11.42}\implies x\approx 1.306 and x\approx-.757.

    Does this make sense?

    --Chris
    kind of. here's what i done.

    Solving 5.71x^2-3.135x-5.64=0, we get x=\frac{3.135\pm\sqrt{138.646}}{11.42}\implies

    I get this part.. but then i divide {138.646}/{11.42} and get -12.141.

    so then i add 3.135+(-12.141) and get -9.006. then subtract 3.135-(-12.141) and get 15.276
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  10. #25
    Junior Member mcdanielnc89's Avatar
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    Quote Originally Posted by skeeter View Post
    no, they are not correct.

    5.71x^2 - 3.135x - 5.64 = 0

    learn to use the store capability of the calculator. the "store" button is just above the ON button labeled [STO->] ... type the number first, hit the store button (you get the arrow), then type in the letter of the alphabet where you want it. A, B, and C are good choices since they represent the values in the quadratic formula.

    5.71 -> A
    -3.135 -> B
    -5.64 -> C

    now type in on the home screen ...

    (-B + \sqrt(B^2 - 4AC))/(2A)
    for one the first root.

    {note that the negative sign in front of B is the small negative sign, whereas the minus sign between B^2 and 4AC is the subtraction sign}

    press [2nd][ENTER] to recall the last expression, change the + to a - ...

    (-B - \sqrt(B^2 - 4AC))/(2A)
    for the second root.

    you should get 1.305586355 and -.7565495776
    you confused me even more.. What number wouldl i type first? i'm totally lost in ur intrucition.
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  11. #26
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    you need to simplify the entire numerator before doing the division. order of operations, remember?

    in any case, why are you doing this piece by piece? that's why you are making errors.

    use the calculator's full capability to evaluate expressions all at once ... work smart, not hard.
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  12. #27
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by mcdanielnc89 View Post
    kind of. here's what i done.

    Solving 5.71x^2-3.135x-5.64=0, we get x=\frac{3.135\pm\sqrt{138.646}}{11.42}\implies

    I get this part.. but then i divide {138.646}/{11.42} and get -12.141.

    so then i add 3.135+(-12.141) and get -9.006. then subtract 3.135-(-12.141) and get 15.276
    This is what you're doing:

    3.135\pm\sqrt{\frac{138.646}{11.42}}\neq\frac{3.13  5\pm\sqrt{138.646}}{11.42}

    To plug this in your calculator, do this:

    (3.135+\sqrt{}(138.646))/11.42

    then hit [2nd] [ENTER] to recall the equation, them make it this:

    (3.135-\sqrt{}(138.646))/11.42

    Then you'll get the answers you are looking for.

    --Chris
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  13. #28
    Junior Member mcdanielnc89's Avatar
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    i forgot to do the square root.. heres the new update


    x=\frac{3.135\pm\sqrt{138.646}}{11.42}\implies


    i get 11.775 out of the square root.

    then i take 3.135 + 11.775 then divide it by 11.42 and get 1.3056 which comes to 1.306

    then i take 3.135 - 11.775 then divide by 11.42 and get -.7565 which comes to -.757
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  14. #29
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by mcdanielnc89 View Post
    i forgot to do the square root.. heres the new update


    x=\frac{3.135\pm\sqrt{138.646}}{11.42}


    i get 11.775 out of the square root.

    then i take 3.135 + 11.775 then divide it by 11.42 and get 1.3056 which comes to 1.306

    then i take 3.135 - 11.775 then divide by 11.42 and get -.7565 which comes to -.757


    --Chris
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  15. #30
    Junior Member mcdanielnc89's Avatar
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    thanks lots chris I'm sure i'll be back. HAHA..
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