The answer is: " 3x² − 17 " .
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f(x) = 3x + 1 ;
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If g(x) = x² − 6 ;
then: (f o g)(x) = f(x² − 6) = 3x + 1 ;
= 3(x² − 6) + 1 = 3x² − 18 + 1 ;
= 3x² − 17 .
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