Fourth root of 128x^7 y^7
Fourth root of 128x^7 y^7
= ⁴√(128x⁷y⁷)
We would then expand (128x⁷y⁷)
= ⁴√(2222222xxxxxxxyyyyyyy)
For every four 2's we bring out one 2 out of the radical, and for every four x's and four y's we bring out one x and one y out of the radical.
= (2xy) ⁴√(222xxxyyy)
= (2xy) ⁴√(8x³y³)
= 2xy ⁴√(8x³y³)
Note the 4 is associated with the radical sign which covers 8x³y³