求函數(shù)的二階導(dǎo)數(shù)。條件極值用求函數(shù)的二階導(dǎo)數(shù)判斷是極大值極小值,即一階導(dǎo)數(shù)的導(dǎo)數(shù)。當(dāng)二階導(dǎo)數(shù)大于0時(shí),表示函數(shù)的斜率在點(diǎn)上升,說(shuō)明點(diǎn)是極小值點(diǎn);當(dāng)二階導(dǎo)數(shù)小于0時(shí),表示函數(shù)的斜率在點(diǎn)下降,說(shuō)明點(diǎn)是極大值點(diǎn)。