Question 830726
{{{S=2pr^2+2pr}}}
{{{S/2p=r^2+r}}}
{{{S/2p+1/4=r^2+r+1/4}}}
{{{S/2p+1/4=(r+1/2)^2}}}
{{{r+1/2= + (S/2p+1/4)}}} and {{{r+1/2= -(S/2p+1/4)}}}
{{{r= -1/2 + S/2p+1/4}}} and {{{r+1/2= -1/2- S/2p-1/4}}}
{{{r= S/2p-1/4}}} and {{{r= -S/2p-3/4}}}