Can expansion and contraction prove all inequalities?

Can expansion and contraction prove all inequalities?

Of course, the expansion and contraction method can not prove all inequalities!
The expansion and contraction method is only a skill, which is commonly used in sequence inequality
In algebraic inequalities, except for absolute value inequalities and some irrational inequalities, scaling method is seldom used to prove them
In trigonometric inequality, sometimes we use scaling method to prove the boundedness of trigonometric function
In geometric inequalities, the scaling technique is seldom used to prove inequalities
In combinatorial geometry, the scaling method is used to prove inequalities