(x+1)(x-1)(x²-x+1)(x²+x+1)
=(x+1)(x²-x+1)((x-1)(x²+x+1)
=(x^3+1)(x^3-1)
=x^6-1
√（9-4√5）
=√（2-√5）^2
=√5-2
2x²+4x-3
=2(x²+2x+1)-2-3
=2(x+1)²-5
=2[(x+1)²-(√10/2)²]
=2(x+1+√10/2)(x+1-√10/2)