a^5+2a^4-17a³-a²+18a-17
=a^4(a+2)-17a³-a²+18a-17
=a³*a*(√17-1+2)-17a³-a²+18a-17
=a³*(√17-1)(√17+1)-17a³-a²+18a-17
=a³*(17-1)-17a³-a²+18a-17
=17a³-a³-17a³-a²+18a-17
=-a³-a²+18a-17
=-a³-2a²+a²+18a-17
=-a²(a+2)+a²+18a-17
=-a*a*(√17-1+2)+a²+18a-17
=-a*(√17-1)*(√17+1)+a²+18a-17
=-a(17-1)+a²+18a-17
=-17a+a+a²+18a-17
=a²+2a+1-18
=(a+1)²-18
=(√17-1+1)²-18
=17-18
=-1