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anonymous

  • 4 years ago

I am so desperate, please help! i have to factor this equation. 21r^2 - rs - 2s^2 As well as solve this one in any way: x^4-21x^2-100=0 Please! The questions are due in 10-15 minutes!

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  1. anonymous
    • 4 years ago
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    (3r-s) (7r+2s) for the first one. (x-5) (x+5) (x^2+4) = 0 x = 5 and x = -5 for the second one. :)

  2. anonymous
    • 4 years ago
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    tlau, how did you get the answer?

  3. anonymous
    • 4 years ago
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    Factor by inspection. Valid method.

  4. jhonyy9
    • 4 years ago
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    x^4 -21x^2 -100 =0 note x^2=y so than y^2 -21y -100=0 y_1,_2=(21+/- sqrt(441+400))/2=(21+/- sqrt(841))/2 =

  5. anonymous
    • 4 years ago
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    wouldn't the answer to the second one also be -4 as well?

  6. anonymous
    • 4 years ago
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    You can't square root a negative number. Have you done imaginary numbers?

  7. anonymous
    • 4 years ago
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    x^2 = -4 No real number x can be squared to get -4. Any number squared positive or negative is positive.

  8. anonymous
    • 4 years ago
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    I did 2 years ago. i'm having to relearn everything as I am starting pre-cal, but now I understand. Thank you very much!

  9. anonymous
    • 4 years ago
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    No problem. :D

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