x²-根号3x-18
=(x²-√3x+3/4)-75/4
=(x-√3/2)²-(5√3/2)²
=(x-√3/2+5√3/2)(x-√3/2-5√3/2)
=(x+2√3)(x-3√3)x的四次平方-2x²-8 因式分解x的四次平方-2x²-8 =(x²-4)(x²+2)=(x-2)(x+2)(x²+2)