X的四次方减6X的二次方+9
=(x²-3)²
=(x+√3)²(x-√3)²
a的四次方减四
=(a²+2)(a²-2)
=(a²+2)(a+√2)(a-√2)
2x的2次方减三
=(√2x+√3)(√2x-√3)