x²-2x-1
=x²-2x+1-2
=(x-1)²-2
=(x-1+√2)(x-1-√2)
2x²+5x+1
=2x²+5x+25/8-17/8
=2(x+5/4)²-17/8
=2(x+5/4+√17/4)(x+5/4-√17/4)