# Chapter 7 - Section 7.4 - Adding and Subtracting Radical Expressions - 7.4 Exercises: 28

$-5\sqrt[3]{ x^2y^2}$

#### Work Step by Step

$\bf{\text{Solution Outline:}}$ To simplify the given radical expression, $3\sqrt[3]{x^2y^2}-2\sqrt[3]{64x^2y^2} ,$ simplify first each term by expressing the radicand as a factor that is a perfect power of the index. Then, extract the root. Finally, combine the like radicals. $\bf{\text{Solution Details:}}$ Expressing the radicand as an expression that contains a factor that is a perfect power of the index results to \begin{array}{l}\require{cancel} 3\sqrt[3]{x^2y^2}-2\sqrt[3]{64\cdot x^2y^2} \\\\= 3\sqrt[3]{x^2y^2}-2\sqrt[3]{(4)^3\cdot x^2y^2} .\end{array} Extracting the roots of the factor that is a perfect power of the index results to \begin{array}{l}\require{cancel} 3\sqrt[3]{x^2y^2}-2(4)\sqrt[3]{ x^2y^2} \\\\= 3\sqrt[3]{x^2y^2}-8\sqrt[3]{ x^2y^2} .\end{array} By combining like radicals, the expression above is equivalent to \begin{array}{l}\require{cancel} (3-8)\sqrt[3]{ x^2y^2} \\\\= -5\sqrt[3]{ x^2y^2} .\end{array}

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