Why isn't 57 a prime number?

Answer 1

#57# is not a prime number, as it has factors other than one and itself.

A prime number is one who does not have any factor other than one and itself.

#57# has #1# and #57# as its factor, but it also has #3# and #19# as its factor.
Hence, #57# is not a prime number.
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Answer 2

#57# is divisible by #3#

#57 = 3xx19#

At first glance #57# would seem to be a prime number ....
after all, #7," "17," "37," "47," "67," "97# are all prime.
Why not #57?#
If you add the digits of #57# you get #5+7 = 12#
#12# is a multiple of #3# This means that #57# is also a multiple of #3#
The nearest multiples of #3# to #57# are:
#60# - which is #3 xx20# and #54# - which is #3xx18#
#57# is #3# away from both of these and is actually #3xx 19#
There are #25# prime numbers from 1 to 100, but there are #5# numbers which warrant extra attention, because they look as though they might be prime but are actually not. Learn them!
These are #" "color(red)(1," "51," "57," "87," "91)#
#1# has only one factor, not two factors as prime numbers have.
#51, 57 and 87# are all multiples of #3#. (add their digits)
#91 = 7 xx13#
As it is a product of two primes and above the normal times tables, we will not often have come across #91# in our maths.
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Answer 3

57 is not a prime number because it has factors other than 1 and itself. Prime numbers are defined as natural numbers greater than 1 that have no positive divisors other than 1 and the number itself. When examining the factors of 57, we find that it can be evenly divided by 1, 3, 19, and 57. Since 57 has factors other than 1 and itself, it does not meet the criteria for being a prime number. Therefore, 57 is a composite number.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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