Formulas and rules
Every key math formula and rule, organised by topic and school level, with examples and study tips.
Functions 5
Function notation
f(x) = ...
A function gives exactly one output for each input.
Linear and affine functions
y = mx + c
m is the slope (steepness), c is the y-intercept.
Slope between two points
m = (y2 - y1) / (x2 - x1)
The slope measures the change in y for each unit of x.
Quadratic functions
y = ax^2 + bx + c
The graph is a parabola. If a > 0 it opens up, if a < 0 it opens down.
Exponential and logarithm
y = a^x ; log_a(a^x) = x
A logarithm answers "what power gives this number".