Factor the expression (72a9b3 − 18a7b5) completely.

a
b3(4a2 − b
)

Factors:

72a^9b^3 - 18a^7b^5

18a^7b^3(4a^2 - b^2)

Common factor of 18a^7b^3:
18a^7b^3(4a^2 - b^2)