To expand and simplify $(x + 3)^2$, we use the identity:

$(a + b)^2 = a^2 + 2ab + b^2$

Here, $a = x$ and $b = 3$, so:

$(x + 3)^2 = x^2 + 2(x)(3) + 3^2$

$= x^2 + 6x + 9$

Thus, the expanded and simplified form is:

$x^2 + 6x + 9$

Would you like a more detailed breakdown?

Here are five related questions to expand your understanding:

1. How do you expand and simplify $(x - 4)^2$?
2. What is the general formula for $(a + b)^2$ and how is it derived?
3. How does the expansion of $(x + 3)^2$ relate to the distributive property?
4. Can you apply the same method to $(2x + 5)^2$?
5. What happens if you expand $(x + 3)(x - 3)$?

Tip: Always remember the identity $(a + b)^2 = a^2 + 2ab + b^2$ to quickly expand squared binomials.