Chapter 7 - Section 7.4 - Adding, Subtracting, and Multiplying Radical Expressions - Exercise Set - Page 439: 33

$3x\sqrt[4]{x^3}$

Using the properties of radicals, then, \begin{array}{l} -2\sqrt[4]{x^7}+3\sqrt[4]{16x^7}-x\sqrt[4]{x^3} \\= -2\sqrt[4]{x^4\cdot x^3}+3\sqrt[4]{16x^4\cdot x^3}-x\sqrt[4]{x^3} \\= -2\cdot x\sqrt[4]{x^3}+3\cdot 2x\sqrt[4]{x^3}-x\sqrt[4]{x^3} \\= -2x\sqrt[4]{x^3}+6x\sqrt[4]{x^3}-x\sqrt[4]{x^3} \\= 3x\sqrt[4]{x^3} .\end{array}