1、 x²-x-1
=x²-x+(1/2)²-5/4
=(x-1/2)²-(√5/2)²
=(x-1/2+√5/2)(x-1/2-√5/2)
2、 2a²-4ab-3b²
=2a²-4ab+2b²-5b²
=2(a-b)²-(√5b)²
=(√2a-√2b+√5b)(√2a-√2b-√5b)
3 -4x^2+4x+11
=-(4x²-4x+1)+11+1
=-(2x-1)²+(2√3)²
=(2√3+2x-1)(2√3-2x+1)
=-(2x+2√3-1)(2x-2√3-1)