Direct and Inverse Proportion (Edexcel GCSE Maths): Flashcards

Is proportional to

Variables increase/decrease together at same rate

$y = kx$ (where $k$ is constant)

Straight line through origin (0,0)

One variable increases as other decreases

$y = \frac{k}{x}$ (where $k$ is constant)

Hyperbola (curved shape)

Doubles too

Halves

$y = kx^2$

$y = \frac{k}{x^2}$

Convert to proportionality statement using $\propto$

Replace $\propto$ with $= k$