Maths AA terms: Q

The formula $x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$, which gives the solutions of the quadratic equation $ax^2 + bx + c = 0$, where $a \neq 0$.

A function of the form $f(x) = ax^2 + bx + c$, where $a$, $b$ and $c$ are constants and $a \neq 0$. Its graph is a parabola.

An inequality such as $ax^2 + bx + c > 0$ or $ax^2 + bx + c \le 0$, where $a \neq 0$. Its solution set is usually an interval or a pair of intervals.

One of the values that divide ordered data into four equal parts: the lower quartile $Q_1$ has a quarter of the data below it, the upper quartile $Q_3$ three quarters.

A non-random sampling method in which the interviewer fills a fixed number (quota) of members from each group of the population, choosing the individuals themselves.

The rule for differentiating one function of $x$ divided by another: if $y = \frac{u}{v}$, then $\frac{dy}{dx} = \frac{v\frac{du}{dx} - u\frac{dv}{dx}}{v^2}$.