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Mathematical Operations

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medium importance~1-2 Q in Tier 15 formulas⚡ 6 shortcuts5 subtopics

Every formula in this topic, grouped by subtopic. Print it and pin it above your desk.

Operator puzzles and BODMAS

BODMAS order
B \to O \to D/M \to A/S

D and M share a rank and resolve left to right; so do A and S.

Substitution map
\{+,-,\times,\div\} \to \{+,-,\times,\div\}

A bijection: rewrite every operator before touching any number.

Hidden-rule and defined operations

Sum of squares
a \# b = a^2 + b^2

Very common hidden rule: 5 # 3 = 34.

Difference of squares
a @ b = a^2 - b^2 = (a+b)(a-b)

8 @ 2 = 60.

Product plus sum
a \$ b = ab + a + b

4 $ 3 = 19.