Equation of a straight line (AQA GCSE Further Maths): Flashcards

$y = mx + c$

Gradient (steepness of line)

Y-intercept (where line crosses y-axis)

$y - y_1 = m(x - x_1)$

$\frac{y - y_1}{y_2 - y_1} = \frac{x - x_1}{x_2 - x_1}$

Same gradient

$-1$

$-\frac{1}{m}$ (negative reciprocal)

$x = 0$

$y = 0$

$\left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right)$

When you know gradient and one point