`y=f(x)` , where `f` satisfies the relation `f(x+y)=2f(x)+x y(y)+ysqrt(f(x))AAx , y in Ra n df^(prime)(0)=0.` Then `f(6)` is equal of `f(-3)` is ________

Explanation

To solve the problem given, we need to analyze the functional equation provided and use the condition given for the derivative at zero. Let's break down the steps to find \( f(6) \) and \( f(-3) \).

### Step 1: Analyze the Functional Equation

We are given the functional equation:

\[
f(x+y) = 2f(x) + xy(y) + y\sqrt{f(x)}
...