Go step by step to reduce the radical.
√ 128

√16 • √8

8 √2

8 √4 • √2

I think its 8×4√16

Explenation:

√128 = 11.3

√16×√8=6.3

8√2= 11.3

so i think you see the patern there and the answer should be 11.3 or 6.3

8√4×√2= 19

19÷2=9.5

9.5÷2=4.75

since 5 is too big to put in the equation and equal 128 then its 4.

To find the second one just do 4², which is 16

So yeah 8×4√16