2a+6a²-4a³=-2a(2a²-3a-1) 解 2a²-3a-1令 2a²-3a-1=0 得 a=[3-√(9+8)]/4 或 a=[3+√(9+8)]/4所以上式可以分解成-2a[a-[3-√(9+8)]/4][a-[3+√(9+8)]/4]
2a+6a^2-4a^3=2a(1+3a-2a^2)=2a(-2a^2+3a+1)=-2a(-a+1)(2a-1)
2a+ 6a2 - 4a3=2a *(1+3a -2a2)