Multiple answers?

I was working on a problem that was presented as 2x²- 10 = 0 I worked it out as such......

2x² - 10 + 10 = 0 + 10
2x² / 2 = 10/2

I came up with x² = 5 now i think that the answer can also be in the form of x = +/- Sqr(5). Now do tests take into acount mathamatical problems that can have answers in multiple forms? Im sure that if a teacher was giving the test he would notice if an answer deviated from a standard form but what about other tests?

it depends on the question. if you get two solutions, make sure they are both valid. If only one is valid, that is your answer. Otherwise, +/-(plus or minus) is the correct answer.

Im going by a algebra review that was handed to me for a college entrance exam which only gives one answer for each problem. The answer was x = +/- Sqr(5). So im trying to figure out if i put x2 = 5 would i have been marked wrong. Maybe im worrying too much. :rolleyes:

The best you could do without asking them what they prefer (hint, hint), is probably towards the end of the question (supposing you're allowed to show your work) is have:

[Show work]
...
x² = 5

Which can be written as
x = +/- sqrt(5)
[/Show work]

I don't know of any prof's who'd mark this wrong, but there are the occasional <insert colorful word here> people who might dock you some marks.

Personally, I'd I'm told to solve for x, I usually write it in the form "x = ....", not "x² = ..." but that's just my 2 cents.

Destined

Yeah, you have to watch out for invalid answers... some might be a real-life-situation when you have to find the maximum area of a rectangle when the perimeter is constant. I think this is a case where there are two answers, one of which would mean a negative perimeter or something. Unless it states negative perimeters are allowed (though I doubt it) then I guess it's safe to just put the positive answer.

However, I lost one mark when they paper asked me to find the square root of the previous question. I only put the positive answer, and since I was penalised I complained and said that it only asked for the square root, and not the roots. When only one root is asked for, it is generally assumed to be the positive one. I won the mark back and so did everyone else who thought like me. But, the negative root is also valid!

My physics teacher told me to read the question at least three times, even if you think you understand it the first time. If you can remember the question off by heart, you'll remember exactly what you're looking for and how to get it.

Thats the way to do it!

If you get marked in a way you disagree, if you argue your case
with the standard book definitions and point out how the
question wasn't specific enough, usually you can win back your
mark.

:)

Thanks for the input guys. Im glad that i have a place to come for help on this stuff. :)