引入参数证明不等式，思路明确，有章可循，是证明不等式的一种重要方法．尤其对不等式取上、下界时，各变元的取值不相等的问题，参数法更显奇效．下面举例说明之．例１　已知正数ａ、ｂ、ｃ，满足ａ＋ｂ＋ｃ＝３，求证：　４ａ＋１＋４ｂ＋１＋４ｃ＋１＞２＋１３．证明　∵ The introduction of parameters to prove inequality, a clear idea, and rules to follow, is an important method to prove inequality. Especially when the upper and lower bounds of the inequality are taken, the value of each variable is not equal, and the parameter method is more effective. The following example illustrates it. Example 1 Known positive numbers a, b, and c satisfy a+b+c=3. Proof: 4a+1+4b+1+4c+1>2+13. Proof ∵