定义1:一般地,我们把形如32y=ax+bx+cx+d(其中a≠0,aübcd均为实数)的函数叫做一元三次函数。一、单调性讨论例1(2012年高考题):已知函数321()3fx=x+x+px,试讨论它的单调性。定理1:设函数ü=()在区间I内可导,则(1)若对任意的x∈I时,füx′>,则:函数ü=()在区间I内为增函数;(2)若对任意的x∈I时,f′üx<,则:函 Definition 1: In general, we call a function of the form 32y = ax + bx + cx + d (where a ≠ 0, aübcd are real numbers) is called a cubic function. First, monotonous discussion Example 1 (2012 college entrance examination questions): Known function 321 () 3fx = x + x + px, to discuss its monotonicity. Theorem 1: Let the function ü = () be guided in the interval I, then (1) if for any x∈I, füx ’>, the function U = () is an increasing function in the interval I; (2) ) For any x∈I, f’üx <, then: letter