2(sin^6t+ cos^6t) - 3(sin^4t + cos^4t) выражение

Решение во вложении-----------------------

2(sin²t+cos²t)(sin^4t-(sintcost)²+cos^4t)-3(sin^4t+cos^4t)=
=2*1*(sin^4t-(sintcost)²+cos^4t)-3(sin^4t+cos^4t)=
=2sin^4t-2(sintcost)²+2cos^4t-3sin^4t-cos^4t)=
=-sin^4t-2(sintcost)²-cos^4t=-(sin^4t+2(sintcost)²+cos^4t)=
-(sin²t+cos²t)=-1