Factoring

A quadratic equation of the form $ax^2+bx+c=0$ can sometimes be solved by factoring the quadratic expression.

When a trinomial is a perfect square, it can be factored into two equal binomials.

When a quadratic is a difference of squares, there is a helpful formula for factoring it.

Polynomials of the form $ax^2+bx+c$ can be factored via the trial and error method.

Completing the square is a common method for solving quadratic equations, and takes the form of $0=a(x-h)^2 + k$.