∵x²+x+1-(x²-1)=x+2>0x²+x+1-(2x+1)=x²-x=x(x-1)>0∴x²+x+1是最长边设x²+x+1所对的角为a∴(x²+x+1)²=(x²-1)²+(2x+1)²-2(x²-1)(2x+1)cosa∴(x²+x...