Answer
$-7\sqrt 2$
Work Step by Step
Simplify. $3\sqrt {18} -4\sqrt {32}$
Therefore, $3\sqrt {18} -4\sqrt {32}=3 \sqrt { 2 \cdot 3 \cdot 3} - 4 \sqrt { 2 \cdot 4 \cdot 4}$
or, $=9\sqrt { 2} - 16 \sqrt { 2}$
Thus, the given radical term can be written as: $-7\sqrt 2$
