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I just cant solve for this unknow, could anyone guild me?

  1. Aug 12, 2009 #1
    I just cant solve for this unknow, could anyone guild me? plz

    1. The problem statement, all variables and given/known data
    It is a problem about VLE from i already found almost everything cept this 2 unknowns i cant solve I need to find A and B but it seems hard to me or i did something wrong

    2. Relevant equations
    Original)
    (1)-------- 0.32=A+lnB
    (2)-------- 0.51=lnA+B


    3. The attempt at a solution
    This is what i have so far
    (1)---------- exp(.32)=exp(A)+B = 1.377
    (2)---------- exp(.51)=A+exp(B) = 1.665

    T_T It confused me. - -
     
  2. jcsd
  3. Aug 12, 2009 #2
    Re: I just cant solve for this unknow, could anyone guild me? plz

    you made a mistake when taking exponentials of both sides.
    so your equations are:
    0.32=A+lnB
    0.51=lnA+B

    when taking exponentials, this gives:
    exp(0.32)=exp(A+lnB)=exp(A)*exp(lnB)=B*exp(A)

    can you do the rest now?
     
  4. Aug 12, 2009 #3
    Re: I just cant solve for this unknow, could anyone guild me? plz

    RHS is wrong remember exp(A + B) = exp(A) * exp(B) remember the rules for exponents.
     
  5. Aug 12, 2009 #4

    Cyosis

    User Avatar
    Homework Helper

    Re: I just cant solve for this unknow, could anyone guild me? plz

    While your manipulations were incorrect even if you do them correctly you still won't be able to solve this algebraically. Seeing as you have decimal values you could try using a graphical calculator to obtain a decimal result.
     
  6. Aug 12, 2009 #5

    Mark44

    Staff: Mentor

    Re: I just cant solve for this unknow, could anyone guild me? plz

    I'm having trouble deciphering your post title. Did you mean you wanted someone to gild you? geld you?

    Oh, now I get it. You wanted someone to guide you.:smile:
     
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