Cube Roots Math Example 3

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Example 3

medium
Simplify 216x63\sqrt[3]{216x^6}.

Solution

  1. 1
    Factor the radicand: 216=63216 = 6^3 and x6=(x2)3x^6 = (x^2)^3, so 216x6=63โ‹…(x2)3216x^6 = 6^3 \cdot (x^2)^3.
  2. 2
    Apply the cube root to each factor: 63โ‹…(x2)33=633โ‹…(x2)33\sqrt[3]{6^3 \cdot (x^2)^3} = \sqrt[3]{6^3} \cdot \sqrt[3]{(x^2)^3}.
  3. 3
    Simplify: 633=6\sqrt[3]{6^3} = 6 and (x2)33=x2\sqrt[3]{(x^2)^3} = x^2. Therefore 216x63=6x2\sqrt[3]{216x^6} = 6x^2.

Answer

6x26x^2
When both the coefficient and the variable part are perfect cubes, the cube root simplifies completely. Use the rule a33=a\sqrt[3]{a^3} = a for any real aa, and note that xn3=xn/3\sqrt[3]{x^n} = x^{n/3} when nn is divisible by 3.

About Cube Roots

The cube root x3\sqrt[3]{x} is the number that, when cubed, gives xx โ€” defined for all real numbers, including negatives.

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