posted by Reisha .
Find the relative extrema of the functions.
take the derivative, set to zero.
the first as an example:
f(x)= 4x (x^2 +1)^-1
f'(x)= 4 (x^2 +1)^-1 -4x(2x)(x^2 +1)^-2
set to zero. Multiply through by (x^2+1)^2
0=4(x^2+1) - 8x^2
x= +- 1/2
what about the second question