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Nonlinear functions SAT question

Math · Advanced Math · Hard · Answer it here, explanation included.

The function is defined by . For what value of does reach its minimum?

ExplanationShow

Choice A is correct. It's given that . Since , it follows that . Expanding the quantity  in this equation yields . Distributing the and the yields . Combining like terms yields . Therefore, . For a quadratic function defined by an equation of the form , where , , and are constants and is positive,  reaches its minimum, , when the value of is . The equation  can be rewritten in this form by completing the square. This equation is equivalent to , or . This equation can be rewritten as , or , which is equivalent to . This equation is in the form , where , , and . Therefore,  reaches its minimum when the value of is .

Choice B is incorrect. This is the value of for which , rather than , reaches its minimum.

Choice C is incorrect and may result from conceptual or calculation errors.

Choice D is incorrect. This is the value of for which , rather than , reaches its minimum.

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