Answer:
[tex]12x^9+15x^8 -8x^6-10x^5[/tex]
Step-by-step explanation:
[tex]~~(x^4)(3x^3 -2)(4x^2 +5x)\\\\=(3x^7-2x^4)(4x^2 +5x)\\\\=12x^9+15x^8 -8x^6-10x^5[/tex]