S1 · Functions · FUNC.LINEAR.PROP

Proportional functions

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Intuition

Understand first, compress later.

A function maps inputs to outputs. Table, formula and graph tell the same relationship in different languages.

Switch representations

Linear functionf(x) = x

graph of fΔx (run)Δy (rise)y-intercept

The line meets the y-axis at 0. From there 2 to the right and 2 up: that ratio is the slope m = 1.

Formal view

You can proportional functions when you can recognise the underlying objects, select valid rules and check each step for equivalence or logical implication.

Why does it work?

This skill sits on a prerequisite network. If a step is unstable, repair the missing prerequisite instead of merely doing more items of the same type.