posted by debby on .
Quadratic equations can be solved by graphing,using the quadratic formula, completing the square, and factoring. What are the pros and cons of the methods. when would each be appropriate?
graphing gives you a ball-park answer, even showing if there are any real solutions
If the equation starts with x^2 and the middle term is even, I ALWAYS use completing the square, it is faster than using the formula and gives you the reduced answer if it is irrational
I often do a quick calculation of the discriminant
b^2 - 4ac on my calculator.
If that answer is a perfect square, then my quadratic will factor,
If the coefficients are single digits I usually look for factors, takes just a few seconds
If the numbers are two digits or "unruly" I just go for the formula way.
This used to be a problem in the past but with today's calculators the difficulty becomes a mute point.