Factorise x3 + x – 3x2 – 3

x³ + x – 3x² – 3

Here x is common factor in x³ + x and – 3 is common factor in – 3x² 3×2 – 3

x³ – 3x² + x – 3

x² (x – 3) + 1(x – 3)

Taking ( x – 3) common

(x – 3) (x² + 1)

Therefore x³ + x – 3x² – 3 = (x – 3) (x² + 1)