When using basic inequalities, we should keep in mind the seven-character mantra of "one positive", "two definite" and "third class". "One positive" means that both formulas are positive numbers, "two definite" means that the sum or product is constant when the basic inequality is applied to find the maximum value, and "three-phase equality" means that if and only if the two formulas are equal, they can be equal.
If the sum of the two formulas in the topic is constant, the sum of the reciprocal of the two formulas is required to be the minimum. Usually this formula is multiplied by 1, and then 1 is expressed by the previous constant.
And expand two formulas to calculate. If the topic is known that the sum of the reciprocal of two formulas is constant, find the minimum value of the sum of the two formulas, and the method is the same as above.
Adjustment coefficient. Sometimes when solving the maximum value of the product of two formulas, the sum of these two formulas needs to be constant, but many times it is not constant. At this time, some coefficients need to be adjusted to make the sum constant.