Question 86316
Try pairing terms:
18{{{a^3}}}– 24{{{a^2}}}b + 15a{{{b^2}}}– 20{{{b^3}}} = 6{{{a^2}}}(3a - 4b) + 5{{{b^2}}}(3a - 4b)
Now, factor out the (3a - 4b) as a common binomial factor:
(3a - 4b)(6{{{a^2}}} + 5{{{b^2}}})