Anonymous
Anonymous asked in Education & ReferenceHomework Help · 8 months ago

I got true for the question but the answer is false can someone please explain why its false? (A − C) − (B − C) = A − B.?

Update:

For this question I drew Venn diagrams for both sides to see if they matched and they didn't. I was told to use a membership table to see why its false. I know membership tables are like truth tables, but how do you make a membership table when there are subtraction signs in the question?

Update 2:

CORRECTION: Sorry I meant I got false for the answer and the correct answer is TRUE. 

3 Answers

Relevance
  • Lôn
    Lv 7
    8 months ago
    Favourite answer

    Remove the brackets...

    A - C - B + C

    = A - B

    YOU are correct.... their answer is wrong.

    • ...Show all comments
    • Lôn
      Lv 7
      8 months agoReport

      Yes, you always have to remove the brackets before you simplify...thanks for BA 👍

    • Commenter avatarLog in to reply to the answers
  • Anonymous
    8 months ago

    Two negatives make a positive so - (-C) is +C.

    Then A - C - B + C and the C's cancel out.

    • Commenter avatarLog in to reply to the answers
  • Mark
    Lv 7
    8 months ago

    Order of operation.  You do the stuff in parentheses first, THEN the rest.  Using (this is just an example) A=5, B=4, and C=1, doing it correctly, the answer would reduce to 1.  Doing it like A-C-B-C will yield -1.

Still have questions? Get answers by asking now.