Add to both sides of the equation:
Square both sides of the equation:
Subtract 3 from both sides:
Multiply both sides by 5:
Divide both sides by 2:
You try to isolate the square root expression all by itself as seen in your previous two questions. That way, you can simply square both sides without having to go through too much algebra.
For the first one:
You can square both sides much more easily than if you did it to the first line.
For the second one, again isolate the square root expression to one side so you can square it.
You made a mortal mistake there. After each step, check the domain and the range! Especially after taking the square of both sides!
You say that,
We could just take the square of both sides and go on and find x=-1.. If hadn't had to be equal to or greater than zero..
You probably made this mistake because you didn't notice that is not the inverse function of .
is never negative.