SOLUTION: What do you think are some downfalls or potential easy mistakes when using the quadratic formula?

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Question 473045: What do you think are some downfalls or potential easy mistakes when using the quadratic formula?



Found 2 solutions by MathLover1, richard1234:
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!

Quadratic Formula is the method for solving quadratic equations that always work. Not only that, but if you can remember the formula it’s a fairly simple process as well.
The important part here is to make+sure that before we start using the quadratic formula that we have the equation in standard form first.
ax%5E2+%2B-x%2B-c=0

At this point we can+identify the values a, b and c for use in the quadratic formula. It is important to make+surethat we carry any minus+signs along with the constants.
There is also some simplification that we can do. We need to be careful however. One of the larger+mistakes in this example x=%282%2B-sqrt%282%29%29%2F2 is to “cancel” to 2’s in the numerator and denominator. Remember that in order to cancel anything from the numerator or denominator then it must be multiplied by the whole+numerator or denominator. Since the 2 in the numerator isn’t multiplied by the whole denominator it can%92t be canceled.
-don’t forget to convert square roots of negative numbers into complex numbers. Also, when+b is negative be very careful with the substitution. This is particularly true for the squared portion under the radical. Remember that when you square a negative number it will become positive. One of the more common mistakes here is to get in a hurry and forget to drop the minus+sign after you square b, so be careful.

Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
The most common mistake is arithmetic errors, especially when multiple minus signs are involved. Or, you might accidentally substitute something wrong, e.g. -b +- sqrt(...) could accidentally be written as b +- ... (I did this in a crucial math competition once...so be careful). Any other type of mistake (e.g. reducing the denominator incorrectly) is extremely rare and shouldn't happen once you've gotten familiar with the quadratic formula.