3(3x³＋2x²－6)²X（9x²+4x）就是先把3x³＋2x²－6当做一个整体求导,再对3x³＋2x²－6求导,然后相乘
y=3x^2-2x^3+6y'=6x-6x^2y'=06x-6x^2=0x=0 or 1y''=6-12xy''(0)=6>0 (min)y''(1)= -6 <0 (max)max y =y(1)=3-2+6=7min y =y(0)=6
