2007-09-29 04:12:50 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
because if you subtract any real number from another real number, the answer will be a real number
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2007-09-29 04:18:25 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Because you can subtract one positive number from another and get a negative number. e.g. if 5 is in the set and 7 is also in the set then for a closed set 5 minus 7 would have to be in the set (i.e. be a positive real number). 5 minus 7 is -2 which is negative and not in the set of positive real numbers. Hence the original set is not closed under subtraction.
2016-04-06 06:52:12 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Hi,
When you subtract, add, or multiply two real numbers, you get a real number. So, these operations are said to be closed. You might be tempted to think that all operations with real numbers are closed, but that is not the case. For example:
Sqrt (-4) = 2i
which is an imaginary number and not a real number. So, the square root operation for real numbers is not closed.
FE
2007-09-29 05:43:26 · answer #3 · answered by formeng 6 · 0⤊ 0⤋
This just mean, if you subtract a real number from a real number, the result will always be another real number.
Real numbers are rational, irrational, positive, negative and zero.
2007-09-29 04:18:06 · answer #4 · answered by Anonymous · 0⤊ 0⤋