20 - 10 and 2 (2 is prime) from 10 do 5 and 2 (both prime)
Factor Tree of 20: ........20 ......../ \ .......4 5 ....../ \ .....2 2
20 10,2 5,2,2
20 10,2 5,2,2
20 10,2 5,2,2
10,2
The purpose of a factor tree is to notate the process of finding the prime factorization. If a number is already prime, a factor tree is not necessary.
20 10,2 5,2,2
20 10,2 5,2,2
20 10,2 5,2,2
The purpose of a factor tree is to divide a number into prime factors. 1 is not a prime number.
10,2 5,2,2
13 is a prime number so it doesn't have a factor tree.