The expression is \(5x - 6x^{2}\). The GCF of the terms \(5x\) and \(-6x^{2}\) is \(x\), since \(x\) is the highest power of \(x\) that divides both terms.
Step 2: Factor Out the GCF
Factor out \(x\) from the expression:
\[
5x - 6x^{2} = x(5 - 6x)
\]
Step 3: Check for Further Factorization
The expression inside the parentheses, \(5 - 6x\), cannot be factored further since it is a linear expression with no common factors.
Final Answer
The completely factored form of the expression is:
\[
\boxed{x(5 - 6x)}
\]