x²-3y²
=x²-(√3y)²
=(x+√3y)(x-√3y)
x²+6x+7
=(x²+6x+9)-2
=(x+3)²-√2²
=[(x+3)+√2] [(x+3)-√2]
=(x+3+√2)(x+3-√2)
4x²-4x-1
=(4x²-4x+1)-2
=(2x-1)²-√2²
=[(2x-1)+√2] [(2x-1)-√2]
=(2x-1+√2)(2x-1-√2)
χ²-3y²
=(x-y√3)(x+y√3)
χ²+6χ+7
=x²+6x+9-9+7
=(x+3)²-2
=(x+3-√2)(x+3+√2)
4χ²-4χ-1
=4x²-4x+1-1-1
=(2x-1)²-2
=(2x-1-√2)(2x-1+√2)