Question 16
Find the least value and the greatest value of the expression
$$
P = x + y
$$
where $x, y$ are real numbers satisfying the condition
$$
x - 3\sqrt{x + 1} = 3\sqrt{y + 2} - y.
$$
$$
P = x + y
$$
where $x, y$ are real numbers satisfying the condition
$$
x - 3\sqrt{x + 1} = 3\sqrt{y + 2} - y.
$$