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ParthKohli

  • 2 years ago

Solve \(x(x + 3) = -9\) NOT by the quadratic formula.

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  1. PeterPan
    • 2 years ago
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    Well, clearly x cannot be positive, as that would mean x+3 is positive too. x must be negative, but no less than -3, or else x+3 would also be negative.

  2. ParthKohli
    • 2 years ago
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    Complex numbers?

  3. ParthKohli
    • 2 years ago
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    I know them by the quadratic formula

  4. PeterPan
    • 2 years ago
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    maybe?

  5. PeterPan
    • 2 years ago
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    Oh, right. I forgot to assume the real-ness of x... I'm lost :D

  6. phi
    • 2 years ago
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    you can complete the square as an alternative to the quadratric formula

  7. PeterPan
    • 2 years ago
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    That's kinda like using the quadratic formula anyway? :D

  8. phi
    • 2 years ago
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    you will get complex roots

  9. ParthKohli
    • 2 years ago
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    Well\[x^2 + 3x + 2.75 = -9 + 2.75\]

  10. PeterPan
    • 2 years ago
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    What's with the 2.75? You mean 2.25, right?

  11. ParthKohli
    • 2 years ago
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    Yes, whoops

  12. sami-21
    • 2 years ago
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    can i use compeleting square ??? or factor mehod ?

  13. ParthKohli
    • 2 years ago
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    \[(x + 1.5)^2 = -9 + 2.25\]Yes, I wanna know how to factor this over \(\mathbb C\) without knowing the roots!

  14. PeterPan
    • 2 years ago
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    It seems like it's already almost done?

  15. sami-21
    • 2 years ago
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    well, i guess this is a good condidate for completing square .

  16. ParthKohli
    • 2 years ago
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    OK, completing the square worked out well. Thanks @phi :-)

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