2008 AMC 10B Problem 3

Below is the professionally curated solution for Problem 3 of the 2008 AMC 10B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2008 AMC 10B solutions, or check the answer key.

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Concepts:exponentradical

Difficulty rating: 940

3.

Assume that xx is a positive real number. Which is equivalent to xx3?\sqrt[3]{x\sqrt{x}}\,?

x1/6x^{1/6}

x1/4x^{1/4}

x3/8x^{3/8}

x1/2x^{1/2}

xx

Solution:

Since x=x1/2,\sqrt{x}=x^{1/2}, we have xx=x1x1/2=x3/2.x\sqrt{x}=x^{1}\cdot x^{1/2}=x^{3/2}.

Taking the cube root multiplies the exponent by 13,\tfrac13, giving (x3/2)1/3=x1/2.\left(x^{3/2}\right)^{1/3}=x^{1/2}.

Thus, the correct answer is D.

Problem 3 in Other Years