ƒ = 6√(128•a^12•b^18•c^6)

First, simplify the numbers under the root:

ƒ = 6√(128•a^12•b^18•c^6)
ƒ = 6√(2^7•a^12•b^18•c^6)

Now, apply the properties of radicals to simplify the expression:

ƒ = 6•2•a^4•b^6•c^2
ƒ = 12•a^4•b^6•c^2

Therefore, the simplified expression is 12•a^4•b^6•c^2.