This equation has no solutions
Move the square root of y to the right hand sides:

To eliminate the roots, let's square both sides. But there is a crucial observation in this passage: you are allowed to deduce
only if both
and
are positive. Otherwise, you risk contraddictions like
.
Since the left hand side is always positive when defined (it's a square root), we need to ask
. So, we're only accept answers if they're greater than nine.
Now we can square both sides:

Simplify y's and bring 9 to left hand side:

Divide both sides by -6:

So, the solution is not acceptable. In fact, it would lead to
