Question 1030357
Find the derivative, I'm substituting a and b for the constants for better readability,
{{{p=(ax)/(b+x)^2}}}
{{{dp/dx=((b+x)^2*a-2ax(b+x))/(b+x)^4}}}

{{{dp/dx=(a/(b+x)^4)(b^2+2bx+x^2-2bx-2x^2)}}}
{{{dp/dx=(a/(b+x)^4)(b^2-x^2)}}}
{{{dp/dx=(a/(b+x)^4)(b-x)(b+x)}}}
{{{dp/dx=(a(b-x))/(b+x)^3}}}
{{{dp/dx=(V^2(R-x))/(R+x)^3}}}
So then when the derivative equals zero,
{{{x=R}}}
and
{{{p=(V^2*R)/(R+R)^2}}}
{{{p=(V^2*R)/(4R^2)}}}
{{{p=V^2/(4R)}}}