-21 , 18

Find the common factors for the numerical part:

-21,18

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.

List the factors for -21.

-21,-7,-3,-1,1,3,7,21

-21,-7,-3,-1,1,3,7,21

The factors for 18 are all numbers between 1 and 18, which divide 18 evenly.

Check numbers between 1 and 18

Find the factor pairs of 18 where x⋅y=18.

xy1182936

List the factors for 18.

1,2,3,6,9,18

1,2,3,6,9,18

List all the factors for -21,18 to find the common factors.

-21: -21,-7,-3,-1,1,3,7,21

18: 1,2,3,6,9,18

The common factors for -21,18 are 1,3.

1,3

The GCF (HCF) of the numerical factors 1,3 is 3.

3

Find the GCF -21 , 18