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Nonlinear Functions

SAT Math· difficulty 4/5

Solve: (13)x=81\left(\dfrac{1}{3}\right)^{x} = 81.

  • A

    x=3x = 3

  • B

    x=−4x = -4

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  • C

    x=4x = 4

  • D

    x=−3x = -3

Explanation

(1/3)x=3−x=81=34(1/3)^x = 3^{-x} = 81 = 3^4, so −x=4⇒x=−4-x = 4 \Rightarrow x = -4.

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