ADD : SUBTRACT :: EXPAND :

1. inflate
2. diminish
3. equate
4. prove

Add and “subtract” are inverse arithmetic operations. “Expand” and “diminish” oppose in scale change. “Inflate” relates to volume, not direct reduction. “Equate” implies equality, not opposition. “Diminish” is the precise antonym for “expand”. So, ADD : SUBTRACT :: EXPAND : DIMINISH