how do i solve v=sqrt(-1-2v)

Solve for v:
sqrt(-1-2 v) = 0

Square both sides:
-1-2 v = 0

Multiply both sides by -1:
2 v+1 = 0

Subtract 1 from both sides:
2 v = -1

Divide both sides by 2:
Answer: |  v = -1/2