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Math Help - Trouble with homework problem

  1. #1
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    Trouble with homework problem

    I am having difficulty with this problem from my homework. Use a graphing calculator to solve the given equation, 4x2 2x 3 = 0. I am missing something here in my method. Without giving the answer can someone show how they would start this problem? I am rusty at this, its been a long time since I has a math course.
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  2. #2
    A riddle wrapped in an enigma
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    Quote Originally Posted by cross1933 View Post
    I am having difficulty with this problem from my homework. Use a graphing calculator to solve the given equation, 4x2 2x 3 = 0. I am missing something here in my method. Without giving the answer can someone show how they would start this problem? I am rusty at this, its been a long time since I has a math course.
    Not knowing what kind of calculator you have, it might be difficult to answer your question.

    Using a TI-84+, enter the equation using the Y= key

    Y_1=4x^2-2x-3

    Press the GRAPH key.

    Press 2nd and then the TRACE key to bring up the CALC menu.

    Choose 2: zero

    Using the left arrow key, move the 'spider' to just above the left x-intercept and press ENTER to mark the left bound side of your zero, then move the spider just below the x-intercept and press ENTER to mark the right bound side of your zero. Press ENTER once more to reveal the zero (x-intercept).

    You should've gotten -.6513878

    That's rounded off, because the exact answer is irrational. Use the quadratic formula to verify this.

    You need to repeat this process for the other zero.

    By the way, the spider is that blinking asterisk of a thing that is tracing the curve when you use the left or right arrow keys.
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  3. #3
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    Quote Originally Posted by masters View Post
    not knowing what kind of calculator you have, it might be difficult to answer your question.

    Using a ti-84+, enter the equation using the y= key

    y_1=4x^2-2x-3

    press the graph key.

    Press 2nd and then the trace key to bring up the calc menu.

    Choose 2: Zero

    using the left arrow key, move the 'spider' to just above the left x-intercept and press enter to mark the left bound side of your zero, then move the spider just below the x-intercept and press enter to mark the right bound side of your zero. Press enter once more to reveal the zero (x-intercept).

    You should've gotten -.6513878

    that's rounded off, because the exact answer is irrational. Use the quadratic formula to verify this.

    You need to repeat this process for the other zero.

    By the way, the spider is that blinking asterisk of a thing that is tracing the curve when you use the left or right arrow keys.
    ti-83
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  4. #4
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    same keystrokes ... 83 is not much different than an 84
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  5. #5
    Senior Member mollymcf2009's Avatar
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    Quote Originally Posted by cross1933 View Post
    ti-83
    It should work with TI-83 the same way.
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  6. #6
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    Quote Originally Posted by cross1933 View Post
    ti-83
    "You should have come up with -.6513878"

    My first calculation came up with X=1.15?
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  7. #7
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    Quote Originally Posted by cross1933 View Post
    "You should have come up with -.6513878"

    My first calculation came up with X=1.15?
    you found the greater root ... note that there is another root at about x = -.65
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  8. #8
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    Quote Originally Posted by skeeter View Post
    you found the greater root ... note that there is another root at about x = -.65
    I picked up a book today(The Complete Idiot's Guide to Precalculus), maybe this will shed some light on the subject. After the problem is over I look back and wonder what I did to get that answer. I think it has to do with confidence, this can only come with repeated work.

    Thanks for the help!
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  9. #9
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    Talking

    The "solutions" are the x-intercepts. So look for where the graph crosses the x-axis.
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  10. #10
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    Quote Originally Posted by stapel View Post
    The "solutions" are the x-intercepts. So look for where the graph crosses the x-axis.
    The answer is right there in front of me. It comes back to lack of confidence from lack of experience. Thanks everyone for your help, I am sure I will be back many times with more questions on different problems.
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