x²-5x+3
=x²-5x+25/4-25/4+3
=(x-5/2)²-13/4
=(x-5/2+√3/2)(x-5/2-√3/2)
x²+2x-1
=x²+2x+1-2
=(x+1)²-2
=(x+1+√2)(x+1-√2)