Let's factorise it :
[tex]\: {\qquad \dashrightarrow \sf ( {x}^{3} - 5)(x + 3) }[/tex]
[tex]\: {\qquad \dashrightarrow \sf {x}^{3} (x + 3) + [-5(x + 3)] }[/tex]
Using Distributive property we get :
[tex]\: {\qquad \dashrightarrow \sf {x}^{3} + {3x}^{3} + ( - 5x - 15) }[/tex]
[tex]\: {\qquad \dashrightarrow \sf {x}^{3} + {3x}^{3} - 5x - 15 }[/tex]
[tex]\: {\qquad \dashrightarrow \sf 4{x}^{3} - 5x - 15 }[/tex]
⠀
Therefore,
[tex]\: {\qquad \dashrightarrow \sf ( {x}^{3} - 5)(x + 3) =4{x}^{3} - 5x - 15}[/tex]
