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Advanced Math / Nonlinear functions Difficulty: Hard

The function g is defined by gx=xa-14, where a<0. What is the product of g15a and g7a?

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Explanation

The correct answer is 609. It’s given that the function g is defined by gx=xa-14, where a<0. Substituting 15a for x in function g yields g15a=15aa-14. This function can be rewritten as g15a=15aa-14, or g15a=15aa-14. Since a<0, it follows that aa=-1. Substituting -1 for aa in g15a=15aa-14 yields g(15a)=15(-1)-14, or g(15a)=-29. Similarly, substituting 7a for x in function g yields g7a=7aa-14. This function can be rewritten as g7a=7aa-14, or g7a=7aa-14. Since a<0, it again follows that aa=-1. Substituting -1 for aa in g7a=7aa-14 yields g(7a)=7(-1)-14, or g(7a)=-21. Therefore, g(15a)=-29 and g(7a)=-21. Thus, the product of g(15a) and g(7a) is (-29)(-21), or 609.