- High school📈Functions🧮
Quadratic equation: the discriminant in 5 seconds
$\Delta = b^2 - 4ac$. Three cases, three scenarios. The universal method for all $ax^2 + bx + c = 0$.
- High school📈Functions📊
Sign table: the method that organizes everything
Study the sign of $f(x)$, solve $f(x) > 0$, understand inequalities: one tool for all these questions.
- High school📈Functions🎯
Absolute value |x|: just the « distance to zero »
No mystery: $|x|$ removes the sign. Two formulations, a geometric use, and $|x|$ inequalities become trivial.
