## Expanding (x + 1)(x + 3) into Standard Form

The expression (x + 1)(x + 3) is in factored form. To write it in standard form, we need to expand it. Here's how:

### Using the FOIL Method

The FOIL method is a mnemonic for remembering how to multiply two binomials:

**F**irst: Multiply the first terms of each binomial.**O**uter: Multiply the outer terms of the binomials.**I**nner: Multiply the inner terms of the binomials.**L**ast: Multiply the last terms of each binomial.

Let's apply this to our expression:

**F:**x * x = x²**O:**x * 3 = 3x**I:**1 * x = x**L:**1 * 3 = 3

Now, we add all the terms together: x² + 3x + x + 3

Combining like terms, we get:

**x² + 4x + 3**

This is the standard form of the expression (x + 1)(x + 3).

### Using the Distributive Property

We can also use the distributive property to expand the expression:

(x + 1)(x + 3) = x(x + 3) + 1(x + 3)

Distributing further:

= x² + 3x + x + 3

Combining like terms, we get:

**x² + 4x + 3**

This confirms that both methods lead to the same answer.

### Conclusion

The standard form of the expression (x + 1)(x + 3) is **x² + 4x + 3**. This form is useful for various algebraic operations, like solving equations, finding the roots of the expression, or graphing the function represented by the expression.