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mydaddysalineman94

  • 4 years ago

Using graphing technology, approximate where the graph of y = 5x2 − 3x − 9 crosses the x-axis. (1.55, 0) and (−1.15, 0) (1.23, 0) and (−1.26, 0) (1.32, 0) and (−1.01, 0) (1.68, 0) and (−1.08, 0)

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  1. brinethery
    • 4 years ago
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    Quadratic formula... a=5 b=-3 c=-9 Plug them in and you'll get two answers for x. Both y-values will be 0.

  2. brinethery
    • 4 years ago
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    Or do you want me to tell you how to do this on a TI-83/84?

  3. mydaddysalineman94
    • 4 years ago
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    I have no idea how to do any of these..:/

  4. brinethery
    • 4 years ago
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    Do you have a graphing calculator?

  5. mydaddysalineman94
    • 4 years ago
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    Nope...

  6. agreene
    • 4 years ago
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    the link I put is a picture of the graph--you can use it to do the estimation they are asking for.

  7. brinethery
    • 4 years ago
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    http://0.tqn.com/d/create/1/0/i/9/9/-/Quadratic.formula.jpg

  8. brinethery
    • 4 years ago
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    a=5 b=-3 c=-9 Plug them in and you'll get two answers for x. Both y-values will be 0.

  9. brinethery
    • 4 years ago
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    (-(-3) +/- sqrt((-3)^2 - 4*5*(-9)))/(2*5)

  10. brinethery
    • 4 years ago
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    (3 +/- (sqrt(9+180))/10 (3+/- sqrt(189))/10 ***THIS MEANS*** x = (3+ sqrt(189))/10 y=0 x = (3-sqrt(189))/10 y=0 Is this making sense?

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