<span>(a+1)(a-1)(a+2)(a-2)-a*(a^2-2a-1) = (a²-1)(a²-4) - a³-2a²-a=a^4-5a²+4</span><span>- a³-2a²-a
</span>
<span>=a^4-a³-7a²-a+4</span>
2х+х=14-3
3х=11
х=11/3=3целых2/3
(2-b)^2 = 2^2 - 2*2*b + b^2 = 4 - 4b + b^2
(3cos(π-x)+sin(π/2+x))/cos(3π+x)=(-3cosx+cosx)/(-cosx)=2cosx/cosx=2