5. If f (x)=(2x+1)^4 then the 4th derivative of f(x)=0 at x = 0 is..

Answer 1

f'=4( )^3 * 2
f"=12 ( )^2 * 2
f'''=24 ( )*2
f""=24*4

So I don't know what your question is, but fourth derivative is not zero.

Answer 2

I think you lost the 2's along the way
f'=4( )^3 * 2
f"=24 ( )^2 * 2
f"'=96 ( )*2
f""=192*2 = 384 (= 24*2^4)