square root(x+1)+ square root(x-1)= square root(2x+1)

square both sides.

(x+1)+(x-1)+2sqrt(x^2-1)=2x+1

2sqrt(x^2-1)=1
square both sides
x^2-1=1/4
x^2=5/4
take the sqrt of each side.
x= 1/2 sqrt 5

check all that.