Respuesta :

3x(4x4 – 5x)
= 12x^5-15x^2
[tex]3x(4x^4-5x)=(3x)(4x^4)-(3x)(5x)=(3\cdot4)x^{1+4}-(3\cdot5)x^{1+1}\\\\=\boxed{12x^5-15x^2}[/tex]