To find the greatest common factor (GCF) of the expression \(20x - 4\), we will first factor out the numerical coefficients and any common variables.
First, we get the coefficients of both terms: \(20\) and \(-4\). The numerical GCF of \(20\) and \(4\) can be found by listing the factors:
- Factors of \(20\): \(1, 2, 4, 5, 10, 20\)
- Factors of \(4\): \(1, 2, 4\)
The greatest common factor among these is \(4\).
Next, we can factor \(20x - 4\) by pulling out the GCF:
\[ 20x - 4 = 4(5x - 1) \]
Thus, the GCF of \(20x - 4\) is \(4\).