Posts
One idea a week, explained properly, with a resource to practise it.
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Chain rule: find the inside function first
Most chain rule mistakes happen before any differentiating starts. Name the inside function first and the rest follows.
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Complex numbers: why one multiplication is a quarter-turn
Multiply a complex number by the imaginary unit and its point rotates a quarter-turn anticlockwise about the origin. Here is why, in three lines of algebra.
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What the slope of a least-squares line actually tells you
Interpreting the slope is a reliable mark in bivariate data questions, and an easy one to lose. Use this sentence template.
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Area models make expanding brackets obvious
If you can multiply two-digit numbers with a rectangle, you can expand a pair of brackets. It is the same picture.