Question 71691
7x^2 + 5x from 9x^2 - 3
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The word "from" indicates to me that you are being asked to subtract {{{7x^2 + 5x}}} from
{{{9x^2 - 3}}}.
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The rule of subtraction is that you change all the signs of the terms in the "take away" 
polynomial, and then add the result to the "take from" polynomial.
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In this case the "take way" polynomial is {{{7x^2 +5x}}}. Change the signs to get:
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{{{ -7x^2 - 5x}}}.
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Then add this to the "take from" polynomial which is {{{9x^2 - 3}}}
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You can only add numbers to numbers and can only add together terms with like powers of x.  
In this case we can add the {{{-7x^2}}} and the {{{+9x^2}}} terms to get (((+ 2x^2))). 
That's one part of the answer.
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Next we have {{{-5x}}} and we need to add it to the "take from" polynomial.  There is no
corresponding term with just an x in the "take from" polynomial, so the {{{-5x}}}
simply adds into the answer set unchanged.  So far our answer is {{{2x^2 - 5x}}}.  
We have a -3 in the "take from" polynomial but there is no corresponding plain-old 
number in the "take away" polynomial to add it to. Therefore -3 appears in the answer set 
unchanged.
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So by combining all the terms in the answer we get an answer of {{{2x^2 - 5x - 3}}}.
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Hope this helps you to understand the problem and the subtraction process a little better.