Answer :
[tex]15a^3+ 20a^2- 6a- 8[/tex]
= [tex]5a^2(3a+ 4) - 2(3a + 4)[/tex]
= [tex](3a+ 4) (5a^2- 2)[/tex]
= [tex]5a^2(3a+ 4) - 2(3a + 4)[/tex]
= [tex](3a+ 4) (5a^2- 2)[/tex]