(а+1)^2 +3 (а-1)^2 -5(а+1)(а-1) выражение

(a+1)²+3(a-1)²-5(a+1)(a-1)=

1) (a+1)²=(a+1)(a+1)=a²+a+a+1=a²+2a+1
2) 3(a-1)²=3(a-1)(a-1)=3(a²-a-a+1)=3a²-6a+3
3) 5(a+1)(a-1)=(5a+5)(a-1)=5a²-5a+5a-5=5a²-5

=(a²+2a+1)+(3a²-6a+3)-(5a²-5)=a²+2a+1+3a²-6a+3-5a²+5=-a²-4a+9