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The Formula Board

Every rule the plots and drills lean on. One board, no guessing.
Signed additionSame signs: add the sizes and keep the sign. Different signs: subtract the sizes and take the bigger number’s sign.
Signed subtractionSubtracting is adding the opposite. Flip the second number’s sign and add.
Sign of a productSame signs make positive, different signs make negative. Division follows the same rule.
Order of operationsGrouping first, then powers, then multiply and divide left to right, then add and subtract left to right.
ExponentsAn exponent counts repeated multiplication: 23 = 2 · 2 · 2.
Distributive propertya(b + c) = ab + ac. The outside number visits everyone inside.
Like termsSame letter part: add the number parts. 3x + 5x = 8x.
One-step equationsUndo what was done to the letter with the opposite operation, on both sides.
Two-step equationsUndo the add or subtract first, then undo the multiply or divide.
RatioA comparison by division. Order matters: 3 to 2 is not 2 to 3.
ProportionTwo equal ratios. The cross products always match.
PercentPercent means per hundred. Move two places to trade with a decimal.
Perimeter and areaPerimeter walks the rim and adds every side. A rectangle’s area is length · width.
Coordinate planeOver first, then up: the ordered pair (x, y).