The given expression is $(x + 1)(x - 3)$. Let's expand and simplify it using the distributive property (also known as FOIL for binomials):

Step-by-step Expansion:

1. Multiply the first terms: $x \times x = x^2$
2. Multiply the outer terms: $x \times -3 = -3x$
3. Multiply the inner terms: $1 \times x = x$
4. Multiply the last terms: $1 \times -3 = -3$

Combine the terms:

$x^2 - 3x + x - 3$

Simplify by combining like terms: $x^2 - 2x - 3$

Final Answer:

$x^2 - 2x - 3$

Would you like more details or have any questions? Here are five related questions you can explore:

1. How do you expand the product of two binomials in general?
2. What happens when you multiply two terms with different signs, like $x \times -3$?
3. Can you factor the expression $x^2 - 2x - 3$ back to its original binomials?
4. How does the distributive property apply when expanding expressions?
5. What are the steps to check if your expansion and simplification are correct?

Tip: Always double-check your work by factoring back to ensure the expansion is correct!