Add or subtract by first simplifying each radical and then combining any like radicals. Assume that all variables represent positive numbers.
--$6\sqrt { 72 }$ + $4 \sqrt {98 }$+9$ \sqrt { 128 }$
A)64$ \sqrt { 2 }$
B)-6$ \sqrt {2 }$
C)-340 $ \sqrt {2 }$
D)340 $ \sqrt { 2 }$

Question

Add or subtract by first simplifying each radical and then combining any like radicals. Assume that all variables represent positive numbers.
--$6\sqrt { 72 }$ + $4 \sqrt {98 }$+9$  \sqrt { 128 }$
A)64$  \sqrt { 2 }$
B)-6$  \sqrt {2 }$
C)-340 $  \sqrt {2 }$
D)340 $  \sqrt { 2 }$

Quizplus · Accepted Answer

First, simplify each radical: $6\sqrt{72} = 6\sqrt{36 \cdot 2} = 6 \cdot 6\sqrt{2} = 36\sqrt{2}$, $4\sqrt{98} = 4\sqrt{49 \cdot 2} = 4 \cdot 7\sqrt{2} = 28\sqrt{2}$, and $9\sqrt{128} = 9\sqrt{64 \cdot 2} = 9 \cdot 8\sqrt{2} = 72\sqrt{2}$. Combining like terms: $-36\sqrt{2} + 28\sqrt{2} + 72\sqrt{2} = 64\sqrt{2}$.

Add or Subtract by First Simplifying Each Radical and Then 6726\sqrt { 72 }672​

Add or Subtract by First Simplifying Each Radical and Then $6\sqrt { 72 }$