Quadratic equations

A quadratic equation has the unknown raised to the second power. Its standard form is $ax^2+bx+c=0$ with $a\neq 0$, and the quadratic formula lets you find its solutions in one stroke. The discriminant $\Delta=b^2-4ac$ tells us at once how many real solutions to expect, without needing to complete the calculations.

• The standard form
• The quadratic formula and the discriminant