Answer:
[tex] {g}^{ - } (x) = 2x + 9 \\ thenthe \: avrage \: equal \: to \: \\ {g}^{ - } (2) - {g }^{ - } ( - 8) = (2 \times 2 + 9) - (2 \times - 8 + 9) \\ = 13 - ( - 7) \\ = 20[/tex]
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