Factor out the GCF: 15a2b+20ab215a^2 b + 20ab^215a2b+20ab2.
5ab(3a+4b)5ab(3a + 4b)5ab(3a+4b)
5a2b2(3+4)5a^2 b^2(3 + 4)5a2b2(3+4)
ab(15a+20b)ab(15a + 20b)ab(15a+20b)
5(3a2b+4ab2)5(3a^2 b + 4ab^2)5(3a2b+4ab2)