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kevingretzky

  • one year ago

use the quadratic formula to find any x-intercepts on the graph of the equation. y=x^2 - 8x -1 x=?

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  1. mathsmind
    • one year ago
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    set y =0, and solve the quadratic equation

  2. mathsmind
    • one year ago
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    \[x ^{2}-8x-1=0\]

  3. ZeHanz
    • one year ago
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    Set a=1, b=-8 and c=-1 in the QF.

  4. mathsmind
    • one year ago
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    \[x=4+\sqrt{17} or x=4-\sqrt{17}\]

  5. mathsmind
    • one year ago
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    yup exactly

  6. mathsmind
    • one year ago
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    you need to use the quadratic formula

  7. mathsmind
    • one year ago
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    \[x=\frac{ -b \pm \sqrt{b^2-4ac} }{ 2a }\]

  8. mathsmind
    • one year ago
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    so the final answer would be

  9. mathsmind
    • one year ago
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    \[(4+\sqrt{17}, 0) and (4-\sqrt{17}, 0)\]

  10. kevingretzky
    • one year ago
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    8 square root 68 over 8?

  11. mathsmind
    • one year ago
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    yup

  12. kevingretzky
    • one year ago
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    is it over 4?

  13. mathsmind
    • one year ago
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    if a =1 yes

  14. kevingretzky
    • one year ago
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    so am i right? it is over 4

  15. mathsmind
    • one year ago
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    over 2x1

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