Work Shown:
x³ + x² + x + 1
(x³ + x²) + (x + 1)
x²(x+1) + 1(x + 1)
(x² + 1)(x + 1)
The basic outline is to pair up the terms into two groups. We factor each group separately, and then factor out the overall GCF (x+1). You can use the FOIL rule to verify the answer.