21 , 3x

Since 21,3x contain both numbers and variables, there are two steps to find the GCF (HCF). Find GCF for the numeric part then find GCF for the variable part.

Steps to find the GCF for 21,3x:

1. Find the GCF for the numerical part 21,3

2. Find the GCF for the variable part x1

3. Multiply the values together

Find the common factors for the numerical part:

21,3

The factors for 21 are all numbers between 1 and 21, which divide 21 evenly.

Check numbers between 1 and 21

Find the factor pairs of 21 where x⋅y=21.

xy12137

List the factors for 21.

1,3,7,21

1,3,7,21

The factors for 3 are all numbers between 1 and 3, which divide 3 evenly.

Check numbers between 1 and 3

Find the factor pairs of 3 where x⋅y=3.

xy13

List the factors for 3.

1,3

1,3

List all the factors for 21,3 to find the common factors.

21: 1,3,7,21

3: 1,3

The common factors for 21,3 are 1,3.

1,3

The numbers do not contain any common variable factors. The GCF (HCF) of the numerical factors 1,3 is 3.

3

Find the GCF 21 , 3x