To answer the question above, raise both sides of the equation to the power of two.
(sqrt (2x + 1))² = 3²
This will simplify into,
2x + 1 = 9
Solving for the value of x gives an answer of x = 4. This value is not an extraneous root as it satisfy the original equation even if it is inside the radical sign. (I hope this is right)
