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Homework Help: Is there any other method to solve this determinant?

  1. Aug 1, 2010 #1
    1. The problem statement, all variables and given/known data
    Row-1......a 1 1
    Row-2......1 b 1
    Row-3......1 1 c

    if the value of the determinant is positive
    the what is abc?

    2. Relevant equations
    ans is abc>-8


    3. The attempt at a solution
    I am not able to follow the method shown in R D sharma Book.
    Is there any other method to solve this determinant?
     
  2. jcsd
  3. Aug 1, 2010 #2

    lanedance

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  4. Aug 6, 2010 #3
    Re: Determinants


    See, you just said that you are not able to follow the method in the RD Sharma book.

    Now, think of this. What USEFUL INFORMATION DOES this convey?

    Can you put the EXACT problem that you face in a MORE INFORMATIVE WAY?

    If you allow me a guess, I assume that the determinant has been expanded into it's factors. After that, what follows is a simple application of Quadratic Expressions (WHICH YOU MIGHT NOT HAVE STUDIED!)

    So, read the solution again, try and paraphrase the steps, and tell us where you face the exact problem!
     
  5. Aug 6, 2010 #4
    Re: Determinants

    I have used some phrases. Let me ReIterate them:

    • Useful Information Conveyed
    • Exact Problem
    • Paraphrase the steps

    Now, keep this post in your notebook or somewhere. Over the next one month, try and think what these three words might mean in different situations.

    Isn't it great how such small and minute things learnt everyday will change you overall as a student? Sahi hai be. Keep learning!
     
  6. Aug 6, 2010 #5
    Re: Determinants

    AFTER EXPANDING THE DETERMINANT,

    The problem reduces to finding the minimum value of abc, if abc + 2 - a - b - c > 0

    Can anyone try their hands at this question? It can be done through the theory of equations!

    Or is there any other method to solve this question from scratch?
     
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