Posted by Yoona on Sunday, February 12, 2012 at 11:19am.
5. If f (x)=(2x+1)^4 then the 4th derivative of f(x)=0 at x = 0 is..

calculus  bobpursley, Sunday, February 12, 2012 at 11:27am
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. 
calculus  Steve, Sunday, February 12, 2012 at 5:03pm
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)