Factorise 15a^2 + ab - 6b^2

15a²+ab-6b²

=(?a+?b)(?a-?b) 

factors of 15= 3 and 5 

factors of 6= 2 and 3 

if we try (3a+2b)(5a-3b) that gives us 15a²+10ab-9ab-6b²  = 15a²+ab-6b²

therefore the answer is (3a+2b)(5a-3b)