答：y=2x^3-6x^2-18x+5求导：y'(x)=6x^2-12x-18=6(x-3)(x+1)零点x1=-1,x2=3再次求导：y''(x)=12x-12=12(x-1)x1=-1,y''(-1)=-240,是极小值点,极小值y(3)=54-54-24+5=-19x3时,y'(x)>0,y(x)是增函数-1...