"a positive": the first step ... a and b must be positive numbers;

[Binary]: Step 2 ............. The product of ……ab must be a fixed value or A+B must be a fixed value;

"Three-phase equivalence": Step 3 ... The equal sign of inequality is true if and only if A = B. ..

It should be noted that there must be a fixed value before it can be used to calculate the fixed value, otherwise, although the inequality is established, the maximum value cannot be obtained.

(Note: Generally, when inequality is applied, the three are judged in turn and hold true at the same time).