set related question ... need confirmation if I am doing this correct :-)

I need some help with understanding this question as well:

==================================== *A – B* = {*x*|*x* ∈ *A* ∧ *x *∉ B}

*A* = {*a, b, e, f*}

*B* = {b, d, g, f, a}

Match the following to the correct answers.

A – B = ?

B – A = ?

Answers:

a. {a, b, f}

b. {a, b, e, f}

c. {d, g}

d. {e}

====================================

What I understand here is that x has elements in A and that those elements are not part of B.

So when we do A - B the correct answer is: c. {a, b, f}

and B - A would be: c. {d, g}

Is this correct?

Thanks,

Re: set related question ... need confirmation if I am doing this correct :-)

Quote:

Originally Posted by

**iwan1981** *A – B* = {*x*|*x* ∈ *A* ∧ *x *∉ B}* A* = {*a, b, e, f*}* B* = {b, d, g, f, a} Match the following to the correct answers. A – B = ? B – A = ?

$\displaystyle A-B=\{e\}$ and $\displaystyle B-A=\{d,g\}$

Re: set related question ... need confirmation if I am doing this correct :-)

Quote:

Originally Posted by

**FernandoRevilla** $\displaystyle A-B=\{e\}$ and $\displaystyle B-A=\{d,g\}$

How did you get this answer ... and what was I doing wrong?

Re: set related question ... need confirmation if I am doing this correct :-)

Quote:

Originally Posted by

**iwan1981** I need some help with understanding this question as well:

==================================== *A – B* = {*x*|*x* ∈ *A* ∧ *x *∉ B}

*A* = {*a, b, e, f*}

*B* = {b, d, g, f, a}

Match the following to the correct answers.

A – B = ?

B – A = ?

Answers:

a. {a, b, f}

b. {a, b, e, f}

c. {d, g}

d. {e}

====================================

What I understand here is that x has elements in A and that those elements are not part of B.

No. x is not a set. It represents a element in A-B. So your statement should be corrected as, "A-B includes all the elements in A which are not in B".

So when we do A - B the correct answer is: c. {a, b, f}

This is incorrect as a,b and f are in B.

and B - A would be: c. {d, g}

Is this correct?

Correct

Thanks,

.

Re: set related question ... need confirmation if I am doing this correct :-)

I understand now ... that's why the ∉ (elements not in) comes into play ... I should've seen that one :-)