Factors of 15 are: 1 3 5 and 15 of which 3 and 5 are prime factors
In doing the factor tree, you can start with any two factors of the given number. These factors maybe prime or composite. But the resulting factors in the factor tree should always be prime numbers. It means that you have to continue factoring unless you ended up with all prime factors.
2 and 13 are the prime factors and the other factors are 1 and 26
34 17,2 (both prime) 2 x 17 = 34
A factor tree shows the prime factors of the working number and can also be used as a visual demonstration to show the prime factors of the working number.
The prime factors are: 5, 5, 3 and 13
44 22,2 11,2,2
As a product if its prime factors: 2*2*5*5 = 100
As a product of its prime factors: 3*5*31 = 465
There is no factor tree nor factors of 57 as it is a prime number.