Solving a quadratic equation when not equal to zero by factoring

The video tutorial explains how to solve the equation 4X = 21 by setting it as a function equal to zero, factoring it, and applying the zero product property to find the zeros. The process involves determining numbers that multiply to -21 and add to -4, leading to the solutions X = 7 and X = -3.

How can you check your answer after factoring the equation?

What are the solutions for the equation X^2 - 4X - 21 = 0?