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nosnip

  • one year ago

Quadratic simultaneous equation PLEASE help me

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  1. nosnip
    • one year ago
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    \[y= x-4\] \[2x ^{2} -xy = 8\] Give your answer in the form a±b sqrt(c)

  2. welshfella
    • one year ago
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    replace the y in the second equation by x - 4 to form a quadratic in x

  3. nosnip
    • one year ago
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    It says I have to use elimination though?

  4. nosnip
    • one year ago
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    Should I make y the subject of both of them and then minus them?

  5. Hero
    • one year ago
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    Multiply the first equation by x

  6. Hero
    • one year ago
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    @nosnip

  7. nosnip
    • one year ago
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    So you get \[x ^{2} - xy - 4x = 0\] \[2x ^{2} - xy - 8 = 0\] Is that right?

  8. nosnip
    • one year ago
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    And then you have to minus them?

  9. Hero
    • one year ago
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    What you want to do is setup the equations in a way where you can combine both together and eliminate the xy term . I try to setup to add rather than subtract

  10. nosnip
    • one year ago
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    So if the plus and minus signs were all reversed and x^2 and 2x^2 were both negative owuld that be better?

  11. Hero
    • one year ago
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  12. nosnip
    • one year ago
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    Got it thankyou so much :)

  13. Hero
    • one year ago
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    What DID you get btw?

  14. nosnip
    • one year ago
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    Well it was a "prove that..." question and I got x^2 +4x - 8 which is what we had to prove so thanks :)

  15. Hero
    • one year ago
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    I thought you had to solve for x in the form a±b sqrt(c)

  16. nosnip
    • one year ago
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    No that was a mistake I have to prove

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