$\"\"$

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Let the polynomial added be A.

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The equation is $\"\"$ .

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$\"\"$ (Subtract $\"\"$ from each side)

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$\"\"$ (Apply commutative property of addition: $\"\"$ )

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$\"\"$ (Apply additive inverse property: $\"\"$ )

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$\"\"$ (Apply additive identity property: $\"\"$ )

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$\"\"$ (Remove brackets)

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$\"\"$ (Apply commutative property of addition: $\"\"$

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$\"\"$ (Subtract: $\"\"$ )

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$\"\"$ (Apply commutative property of addition: $\"\"$

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$\"\"$ (Subtract: $\"\"$ )

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The polynomial to be added is $\"\"$ . $\"\"$

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The polynomial to be added is $\"\"$ .