Published
Edited
Sep 17, 2019
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## Algebra
|Name|Rule|Example|
|-|-|-|
|Difference of squares|${tex`a^2 - b^2 = (a+b) \times (a-b)`}|TBC|
|Triangle numbers|${tex`T(n) = n(n-1) \div2`}|gives the nth triangle number|
|Pentagonal numbers|${tex`P(n) = T(n) + 2T(n-1) = T(n) + (n -1)n = n(n-1) \div 2 + (n-1)n`}|TBC|
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## Logic
### Implication
|Statement|Example|Truthfulness|
|-|-|
|Implication|if A then B|
|Contrapositive|If not B then not A|Always true|
|Converse|If B then A|Maybe true|
|Inverse|If not A then not B|Maybe true|
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Purpose-built for displays of data
Observable is your go-to platform for exploring data and creating expressive data visualizations. Use reactive JavaScript notebooks for prototyping and a collaborative canvas for visual data exploration and dashboard creation.
