Answer: 4a
Explanation:
12a²b⁶ 28a⁴ 42ab³
∧ ∧ ∧ ∧ ∧ ∧
2 6 a² b⁶ 7 4 aaaa 7 6 a b³
∧ ∧ ∧ ∧ ∧
2 3 aa bbbbbb 2 2 2 3 bbb
12a²b⁶: 2 * 2 * 3 * aa * bbbbbb
28a⁴: 2 * 2 * 7 * aaaa
42ab³: 2 * 2 * 3 * 7 * a * bbb
What do they have in common? two 2s and one a
GCF = 2 * 2 * a = 4a