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Math Help - Solving the system of two equations in two unknowns

  1. #1
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    Solving the system of two equations in two unknowns

    I'm going through these tutorials for Calc III, and I came upon this slide:

    main-22.pdf

    source:MATH 311 - Calculus III Resources

    How did the author solve for s and t?
    Last edited by Lexy; April 12th 2012 at 05:46 PM.
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  2. #2
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    Re: Solving the system of two equations in two unknowns

    Quote Originally Posted by Lexy View Post
    I'm going through these tutorials for Calc III, and I came upon this slide:

    main-22.pdf

    source:MATH 311 - Calculus III Resources

    How did the author solve for s and t?
    first equation ...

    1 + t = 2s , solve for t

    t = 2s - 1

    substitute (2s - 1) for t in the second equation ... solve for s, then determine the value of t
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  3. #3
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    Re: Solving the system of two equations in two unknowns

    That's one good method. Another is this: the two equations are 1+ t= 2s and -2+ 3t= 3+s. Multiply the first equation by 3 to get 3+ 3t= 6s. Now subtract the second equation from that: (3+ 3t)- (-2+ 3t)= 6s- (3+ s). The "t" terms cancel giving 5= 5s- 3. Solve that for s then put that value into either of the original equations to get an equation to solve for t.
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