# Find the GCF a^4b , -ab^2 a4b , -ab2
Since a4b,-ab2 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 a4b,-ab2:
1. Find the GCF for the numerical part 1,-1
2. Find the GCF for the variable part a4,b1,a1,b2
3. Multiply the values together
Find the common factors for the numerical part:
1,-1
The factors for 1 are 1.
The factors for 1 are all numbers between 1 and 1, which divide 1 evenly.
Check numbers between 1 and 1
Find the factor pairs of 1 where x⋅y=1.
xy11
List the factors for 1.
1
1
The factors for -1 are -1,1.
The factors for -1 are all numbers between 1 and 1, which divide -1 evenly.
Check numbers between 1 and 1
Find the factor pairs of -1 where x⋅y=-1.

List the factors for -1.
-1,1
-1,1
List all the factors for 1,-1 to find the common factors.
1: 1
-1: -1,1
The common factors for 1,-1 are 1.
1
The GCF for the numerical part is 1.
GCFNumerical=1
Next, find the common factors for the variable part:
a4,b,a,b2
The factors for a4 are a⋅a⋅a⋅a.
a⋅a⋅a⋅a
The factor for b1 is b itself.
b
The factor for a1 is a itself.
a
The factors for b2 are b⋅b.
b⋅b
List all the factors for a4,b1,a1,b2 to find the common factors.
a4=a⋅a⋅a⋅a
b1=b
a1=a
b2=b⋅b
The common factors for the variables a4,b1,a1,b2 are a⋅b.
a⋅b
The GCF for the variable part is ab.
GCFVariable=ab
Multiply the GCF of the numerical part 1 and the GCF of the variable part ab.
ab
Find the GCF a^4b , -ab^2     