Chapter Summary

Key results

• A Cartesian plane locates any point as an ordered pair $(x, y)$.
• A function gives one output per input: $y = f(x)$.
• A linear function $y = mx + c$ graphs as a straight line.
• Gradient $= \dfrac{y_2 - y_1}{x_2 - x_1}$: positive rises, negative falls, zero is flat.
• Finding the equation from two points: find $m$, then substitute one point for $c$.
• Horizontal: $y = k$, gradient $0$. Vertical: $x = h$, gradient undefined.
• In context: gradient $=$ rate of change, $y$-intercept $=$ starting value.