Question 846042
{{{r^2-2r-15=0}}}
{{{(r^2-2*r*1+1^2)-1^2-15=0}}}
{{{(r-1)^2-1-15=0}}}
{{{(r-1)^2=16}}}
{{{x = 1 +- sqrt(16)}}}
{{{x = 1 +- 4}}}
{{{x = -3}}},{{{5}}}

Your other answers look correct!