1)(a-b)-(a-b)(a²+ab+b²)=(a-b)(1-a²-ab-b²)
2)(a²+3a+2)(a-3)-a²+4a+5=a³-3a²+3a²-9a+2a-6-a²+4a+5=a²-a²+3a-1
Cos^2(pi/12)+sin^2(pi/12) = <span>cos^2(pi/12)+(1 - cos^2(pi/12) ) =
= (</span>cos^2(pi/12) - cos^2(pi/12) ) +1 = 0 + 1 = 1
(у+7)²-14у=у²+14у+49-14у=у²+49.