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Homework Help: Homework problem

  1. Jan 27, 2010 #1
    1. The problem statement, all variables and given/known data

    Express the number in the form a/b

    2. Relevant equations

    [tex] -2^{4} + 3^{-1} [/tex]

    3. The attempt at a solution


    16+(-3) = 13

    Why is this not the correct answer?
     
  2. jcsd
  3. Jan 27, 2010 #2
    1) should the negative sign in the term -2^4 be inside the bracket? should it be (-2)^4? If yes then 16 is correct.

    2) for any number, say x, x^(-1)=1/x not -x.

    can you do it now?
     
  4. Jan 27, 2010 #3
    Well if the negative sign is outside as such: -(2^4), does that make it a -16 instead of positive?
     
  5. Jan 27, 2010 #4
    yes.

    so what do you get for the answer?
     
  6. Jan 27, 2010 #5

    Mark44

    Staff: Mentor

    Yes, as opposed to (-2)4, which is 16.

    Both what you have written, -(24), and -24 are equal to -16.
     
  7. Jan 27, 2010 #6
    47/3.

    After you told me 3^-1 was not -3 but instead 1/3, i was able to figure it out. I cross multiplied -16 with 1/3 and i came out with 48 then when i added the fraction i came out with 47/3. does it sound right?
     
  8. Jan 27, 2010 #7
    you cross multiplied??

    you just have to add -16 to 1/3.

    I think you have the answer...you just forgot a minus sign...right? ;)
     
  9. Jan 27, 2010 #8
    This problem is giving me trouble. The correct answer is 47/3. I just can't figure out how to arrive at it. I thought i could arrive by cross multiplying, but looking at it again, it doesnt seem right.
     
  10. Jan 27, 2010 #9

    Mark44

    Staff: Mentor

    Are you sure you have given us the problem verbatim? The answer to the problem you posted is -47/3, not 47/3.

    -24 + 3-1 = -16 + 1/3 = -48/3 + 1/3 = -47/3

    To get a common denominator of 3, you multiply -16 by 1 (in the form of 3/3) to get -48/3. Now both denominators are 3 and you can add the numerators.
     
  11. Jan 27, 2010 #10
    Yes sorry i meant to say -47/3. I wasnt sure how you arrived at -48/3 but i realize i forgot about finding the common denominator
     
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