The last one. And I did answer for you too.
Answer:

Explanation:
In the first example the division results in a radical, not a polynomial.
The remaining examples are not counter-examples (they do result in a polynomial)
Answer:
uit is the mixed number of decimal point
(2x+3y)+(7x-3y)
First, group like terms together, so (2x+7x) + (3y-3y). Then simplify within the parentheses. 2x+7x = 9x and 3y-3y = 0, so you have 9x, which cannot be simplified any further. The answer is 9x.
Answer:
B. f(x) = 3/(x^2 +2x +1)
E. f(x) = 5/(3+x)
Step-by-step explanation:
The above functions have denominators that are zero at one point. For B, that point is x=-1; for E, that point is x=-3. When the denominator is zero, the function is undefined, so the corresponding x-value must be excluded from the domain.
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As written, choice D also qualifies. This is because the function written in the answer list here is ...

It will be undefined for x=0.
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<em>Comment on writing rational functions</em>
When the division symbol (/ or ÷) is used with a denominator that is a product or sum, that product or sum must be enclosed in parentheses. When the expression is typeset, the division bar acts as a grouping symbol. When the expression is written in text, a grouping symbol, such as parentheses, must be added.