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-   -   Elimination or Substitution and how do I do it? (https://www.askmehelpdesk.com/showthread.php?t=175499)

  • Jan 22, 2008, 06:10 PM
    Median_Blow
    Elimination or Substitution and how do I do it?
    ^=exponent

    y^2=25
    x^2-2x=4x+16




    :eek:
  • Jan 22, 2008, 08:00 PM
    jiten55
    Neither!

    You have 2 unrelated equations.

    From y^2 = 25 you get values of y

    (Hint: if x^2 = 49, x = 7 or -7)

    x^2-2x=4x+16

    Becomes x^2 -6x -16 = 0

    Which is a quadratic equations, which in this case can be solved by factorising, or
    by the formula for quadratic equations.

    Hint for factorising: Find 2 numbers (a and b) whose product is -16 and whose sum is -6.

    Then factorising gives you (x -a) (x-b) = 0

    from which you get 2 values of x: a and b.

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