(d − 30)(d + 30) − 7 = −7 What is a solution to the given equation?

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The correct answer is either −30 or 30. Adding 7 to each side of the given equation yields (d − 30)(d + 30) = 0. Since a product of two factors is equal to 0 if and only if at least one of the factors is 0, either d − 30 = 0 or d + 30 = 0. Adding 30 to each side of the equation d − 30 = 0 yields d = 30. Subtracting 30 from each side of the equation d + 30 = 0 yields d = −30. Therefore, the solutions to the given equation are −30 and 30. Note that −30 and 30 are examples of ways to enter a correct answer.

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