不等式成立问题,是高考考查的重要内容.这类问题内容丰富,概括起来有恒成立、能成立、恰成立、部分成立四种类型.一、恒成立例1若函数f(x)=x3-b2x2+bx+c在区间[-2,1]上单调递增,求b的取值范围.解函数y=f(x)在区间[-2,1]上单调递增,又f′(x)=3x2-bx+b.依题意,恒有f′(x)≥0,即3x Inequality is the establishment of the college entrance examination exam is an important part of the content of these questions rich in content, summed up a permanent establishment, can be established, just established, in part the establishment of four types. First, Heng established Example 1 If the function f (x) = x3-b2x2 + bx + c increases monotonically in the interval [-2,1] and finds the range of b. The solution function y = f (x) increases monotonically in the interval [-2,1] 3x2-bx + b. According to the meaning, there is f (x) ≥0, that is 3x