Question 896918
{{{sqrt(y) + sqrt(y+4) = 3}}}

square it

{{{(sqrt(y) + sqrt(y+4))^2 = 3^2}}}

{{{y +2*sqrt(y(y+4)) +(y+4) =9}}}

{{{sqrt(y(y+4)) = (5 - 2y)/2}}}

square again 

{{{y(y+4) = ((5 - 2y)/2)^2}}}

{{{4y^2 + 16y = 25 -20y + 4y^2}}}

{{{36y = 25}}}

{{{y =25/36}}}