(2a + b)(a-1) la patrat -(a-1) la patrat * b =(2a+b)(a²-2a+1)-(a²-2a+1) xb==2a³-4a²+2a+ba²-2ab+b-(a²b-2ab+b)=
=2a³-4a²+2a+ba²-2ab+b-ba²+2ab-b (vezi ca ba² sau a²b este unul si acelasi lucru de asta am scris in loc de a²b=ba²)
=2a³-4a²+2a+ba²-ba²-2ab+2ab+b-b=
=2a³-4a²+2a=2a(a²-2a+1)=2a(a-1)²
(x+2) la patrat - x-2= x²+4x+4-x-2=x²+3x-2
