Solve a Quadratic (in Disguise)
(Purdue University)

Solve the following equation for x:

The student must recognize that this is a quadratic equation, but for y = x2 (and not for x). The first step is to solve .

One solution, y = -9, gives a pair of complex solutions: x = ±3i. The other solution, y = +4, gives a pair of real solutions: x = ±2. These are the four solutions to the original equation.