X2-21x+84=0 that's xsquared (x- ? )(x- ? )

Answer 1

In google type:
quadratic equation online

When you see list of results click on:

Free Online Quadratic Equation Solver:Solve by Quadratic Formula

When page be open in rectangle type:

x^2-21x+84=0

and click option solve it

You will see solution step-by-step