[tex]20f^3 -24f^2 -35f+42\\\\=4f^2(5f-6) -7(5f-6)\\\\= (5f-6)(4f^2-7)[/tex]
[tex]\sf \longmapsto \: 20f {}^{3} −24f^2+42−35f[/tex]
[tex]\sf \longmapsto20f^3−24f^2−35f+42[/tex]
[tex]\sf \longmapsto \: (5f−6)(4f^2−7)[/tex]
[tex] \sf \: (5f−6) \times (4f^2−7)[/tex]
