Which of the following best defines the greatest common factor (GCF) for a list of algebraic terms?

Find the GCF of the integers 84 and 126 using prime factorization.

A company's profit per period is modeled by $P\left(t\right)=12t^3+18t^2-6t$. Factor the expression by extracting the GCF, interpreting $t$ as time in periods.

Factor completely: $4x^3-8x^2+6x-12$

Which factoring strategy is most efficient for $x^4-16$, and what is the complete factorization?