# Quick function question

Can anyone explain why the +3 in this function is changed into a negative 3?  Here is the function:

(f - g)(x) = f(x) - g(x) = 2x^2 - 1 - (5x + 3)
=2x^2   - 1 - 5x - 3   <----- not sure why this is now -3
=2x^2 -5x -4 is the answer

Thanks
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Fixer of ProblemsCommented:
- (5x + 3) is the same as -1 times (5x + 3).  That is equal to - 5x - 3.
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Author Commented:
So that is not the order of operations but its assumed that there is a -1 in front of the parenthesis?
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Fixer of ProblemsCommented:
By definition, a '-' in front of a value is the same as multiplying by -1.  The () groups the 5x + 3 as a single value so the '-' is applied to both when you remove the ().
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The order of operations is the same in your example as the -1( ) is -( ) as noted by Dave.
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Fixer of ProblemsCommented:
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Author Commented:
Thanks :)
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Author Commented:
I may have a lot more questions.  Preparing for an important math exam and I have been out of school for 25 years.  Very rusty indeed!
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Get a first year algebra book as this stuff is covered nicely in such a book. I have a bunch in the basement from university days.
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Fixer of ProblemsCommented:
I agree with John.  When I went back to college (a long time ago), I picked up several of the 'Made Simple' math books.  They were great.  They had all the rules for algebra or geometry listed in the front or the back of the books where you could easily see how they related.  That site I linked to, http://www.algebrahelp.com/ , looks pretty good too.
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Author Commented:
Thanks guys, much appreciated!
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Fixer of ProblemsCommented: