Question 96890
{{{x+3=sqrt(x+15)}}}
Square both sides. {{{(x+3)^2=x+15}}}
{{{x^2+6x+9=x+15}}}
subtract x+15 from both sides. {{{x^2+5x-6=0}}}
(x-1)(x+6)=0
x=1 x=-6
Check:
{{{1+3=sqrt(1+15)}}} ok
{{{-6+3=sqrt(-6+15)}}}
{{{-3<>3}}}
x=1 is the only correct answer. 
Ed