Chapter 7 - Section 7.4 - Adding, Subtracting, and Multiplying Radical Expressions - Exercise Set - Page 439: 55

$\sqrt[3]{a^2}+\sqrt[3]{a}-20$

Using $(a+b)(c+d)=ac+ad+bc+bd$ or the FOIL method, then, \begin{array}{l} \left( \sqrt[3]{a}-4 \right)\left( \sqrt[3]{a}+5 \right) \\= (\sqrt[3]{a})(\sqrt[3]{a})+(\sqrt[3]{a})(5)+(-4)(\sqrt[3]{a})+(-4)(5) \\= \sqrt[3]{a^2}+5\sqrt[3]{a}-4\sqrt[3]{a}-20 \\= \sqrt[3]{a^2}+\sqrt[3]{a}-20 .\end{array}