Factor the expression 20a3b7 − 12a2b9 completely.
a a2b7(20a − 12b2)
b 4(5a3b7 − 3a2b9)
c 4a2b7(5 − 3b)
d 4a2b7(5a − 3b2)
The correct answer is b) 4(5a^3b^7 - 3a^2b^9).
To factor the expression 20a^3b^7 - 12a^2b^9 completely, we can factor out the greatest common factor from both terms, which is 4a^2b^7.
Therefore, 20a^3b^7 - 12a^2b^9 = 4a^2b^7(5a - 3b^2) = 4(5a^3b^7 - 3a^2b^9)