Răspuns:
(X+1)(X³+X²+X-1)=X^4+X³+X²+X-1=X^4+2X³+2X²-1
(x+1) (x³+x²+x-1)=
x·x³+x·x²+x·x-x+x³+x²+x-1=
x⁴+x³+x²-x+x³+x²+x-1=
x⁴+x³+x²+x³+x²-1=
x⁴+2x³+x²+x²-1=
x⁴+2x³+2x²-1
---→ΔTriunghiul₁Δ←---
