If k is an integer, what is
k + 1
/2
!
? Why?

If than however any divided by 2 is in .

But it is not so simple.

If is odd then is even but when even number is divided by 2, you get an odd number which is in .

However if is even then is odd and when we divide that by 2, you get a number like for example which is not in but rather inside . There are fortunately no irrational numbers.

There is also a problem with zero, zero is neither odd nor even but still an integer. If your happens to be -1, , and zero divided by 2 is still just 0 which is in .

So to sum up,

If is odd and not -1, then .

Or to put it in math .

If is even or -1, then .

Or to put it in math .

Notes:

is a set of integers.

is a set of rational numbers.

means integers are a subset of rational numbers, that is, every integer is a also a fraction, however not every fraction is an integer.

Hope this helps :)

answer: c.  

step-by-step explanation:

mixtures containing substances that get attracted to magnet can be separated using a magnet. we can separate iron from a mixture of sand and iron, as only iron attracts to the magnet.