Which operation is not closed for polynomials? a) (x3 + 8x − 5) (x4 + 6x + 2) b) (x2 + 4x − 5)(8x2 + 3x − 6) c) (6x2 + 2x − 3) + (x2 − 5x + 4) d) −(2x2 + 2x − 5) − (x2 + 2x + 9)

A

Step-by-step explanation:

You had a typo with A, and I think that is the answer as well, seeing as you typed all of your other answers correct, and none of them were labeled open by the first answerer, despite the typo.

in problems involving proportions, we can use cross products to test whether two ratios are equal and form a proportion. to find the cross products of a proportion, we multiply the outer terms, called the extremes, and the middle terms, called the means.

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1/3 + 1/5 = 8/15.

step-by-step explanation:

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