9514 1404 393
Answer:
C. 6x² +20x +30
Explanation:
The perimeter of a rectangle is given by the formula ...
P = 2(L +W)
Substituting the given length and width, you have ...
P = 2((3x² +7x +9) +(3x +6))
Simplifying gives ...
P = 2(3x² +10x +15)
P = 6x² +20x +30
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Additional comment
"Standard form" has the terms in order of decreasing exponents. The expression of choice D is equivalent, but is not in standard form.