[tex] 4\sqrt[4]{128} [/tex]
We can simplify the 128 under the fourth root sign. Since 2^4 is 16, and 128 is divisible by 16, we can pull that out of the radical.
[tex] 4\sqrt[4]{128} = 4\sqrt[4]{16*8} = 4\sqrt[4]{2^4 * 8} = 4*2\sqrt[4]{8} = 8\sqrt[4]{8} [/tex]
