If a and B are prime numbers, then M = a * B must be a composite number Is that right

If a and B are prime numbers, then M = a * B must be a composite number Is that right

For example, 15 = 3 * 5, so 15 is not a prime. For another example, 12 = 6 * 2 = 4 * 3, so 12 is not a prime. On the other hand, 13 is not a prime except 13 * 1

If M = a × B × C, where a, B and C are prime numbers, then the sum of M prime factors has

Let me try
If a, B and C are all prime numbers, then I (≥ 2) multiplication results from the total number are composite numbers
For every prime number, there are two cases of taking and not taking, 2 ^ 3,
But one of them is not a composite number, so we need to get rid of the case that none of them is taken, and three cases that only one is taken
There are 2 ^ 3-3-1 = 4 composite factors

The factor of 18 is______ Where prime numbers are______ The total number is______ ．

The factors of 18 are 1, 2, 3, 6, 9 and 18. The prime numbers of 18 are 2 and 3, and the total numbers are 6, 9 and 18. So the answers are 1, 2, 3, 6, 9, 18, 2, 3, 6, 9 and 18

The factor of 18 is______ Where prime numbers are______ The total number is______ ．

The factors of 18 are 1, 2, 3, 6, 9 and 18. The prime numbers of 18 are 2 and 3, and the total numbers are 6, 9 and 18. So the answers are 1, 2, 3, 6, 9, 18, 2, 3, 6, 9 and 18

The factor of 18 is (), of which the factor which is both prime and even is ()

The factors of 18 are (1,2,3,6,9,18). Among these numbers, the factor that is both prime and even is (2)

Let's take 18 and find their least common multiple

18=2*3*3
20=2*2*5
Their least common multiple = 2 * 3 * 3 * 2 * 5 = 180

A is the multiple of B, C is the factor of B, (a, B, c) = (), [a, B, C] = ()

A is the multiple of B, C is the factor of B, (a, B, c) = (c), [a, B, C] = (a)

A is a multiple of B, B is a multiple of C, and C is a factor of A

Yes
A is the factor of B, which means that a and B are integers and there is an integer k such that B = Ka,
B is the factor of C, which means that C is also an integer and there exists an integer m such that C = MB,
So C = MB = MKA,
Let μ = MK, because m and K are integers, μ must be integers
So C = μ a, that is, C is a multiple of A

A is the factor of B, B is the factor of C, so C is a multiple of A

Yes
A is the factor of B, which means that a and B are integers and there is an integer k such that B = Ka,
B is the factor of C, which means that C is also an integer and there exists an integer m such that C = MB,
So C = MB = MKA,
Let μ = MK, because m and K are integers, μ must be integers
So C = μ a, that is, C is a multiple of A

If a is a factor of B and C is a multiple of B, then the least common multiple of a, B and C is

It's C
A is the factor of B, that is, B includes a, and the multiple of B must be the multiple of a; C is the multiple of B, that is, C includes B and C, so the least common multiple of a, B and C is C
C includes B and B includes a, so C includes B and a