Question

How do you decide when to use the 'completing the square' method when solving a quadratic equation?

Answer 1

When you canoot factor the quadratic

Answer 2

* cannot

Answer 3

Once mastered, "completing the square" is pretty straightforward. I like it. View it as one of many options for solving a quadratic equation. Easiest when the constant coeff. of the x^2 term is 1; dicier (but possible) when that coeff. is greater or smaller than 1. If you want practice, submit a quadratic and we'll complete the square and compare that sol'n to one found via some other method.

Answer 4

When a quick look rational roots produces no immediate solution, completing the square, or its offspring, the quadratic formula should come to mind. I like to calculate the discriminant, first, and make fun of myself if I just missed the rational roots.

Answer 5

ok

Answer 6

...

Answer 7

is there any other reason other than if the quadratic equation is not factorable?

Answer 8

Sure,

Ii might be demanded on an exam.
It might impress your classmates.
You might need the practice.
You could save the planet if hostile Martians come by and threaten to blow up Earth if you can't demonstrate "Completing the Square".
You may need to get a parabola in vertex form.
You may need to adjust an integral so a certain substitution will work.

My point -- what difference does it make? It's a method that ALWAYS works. It's interesting. It's a skill that could help you in future math class. Don't try to make boxes into which to put methods and problems. Keep your mind open. Keep it all in front of you.