Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Question about Sets

  1. Jan 11, 2007 #1
    1. The problem statement, all variables and given/known data
    Here is the problem that I want to make sure I have an understanding of:

    (A intersects B) - C

    Given the following sets: A= {1,4,7,10} B= {1,2,3,4,5} C= {2,4,6,8}

    Order of operations tells me to do what's in parentheses first. A intersecting B which gives me {1, 4}

    Now minus C is where I'm a little fuzzy - I think the final answer is {4} because I took out the number that wasn't in set C - being 1.

    Am I on the right track?
     
  2. jcsd
  3. Jan 11, 2007 #2

    matt grime

    User Avatar
    Science Advisor
    Homework Helper

    What is the definition of X\Y or X-Y in your notes?
     
  4. Jan 11, 2007 #3
    The difference X - Y consists of all elements in X that are not in Y
     
  5. Jan 11, 2007 #4

    matt grime

    User Avatar
    Science Advisor
    Homework Helper

    So apply the definition to the sets.
     
  6. Jan 11, 2007 #5
    Right - so the answer is 4
     
  7. Jan 11, 2007 #6

    HallsofIvy

    User Avatar
    Science Advisor

    ???
    YOU just said "The difference X - Y consists of all elements in X that are not in Y" (added emphasis). So (A intersect B)- C consists of all elements of (A intersect B) that are not in C. And C= {2, 4, 6, 8}.
    Which of 1 and 4 is not in C?
     
  8. Jan 11, 2007 #7
    Okay - I had it backwards - 1 is not in C
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook