The expression $\frac{a + b}{a + b}$ simplifies as follows:

• If $a + b \neq 0$, then the expression simplifies to 1 because any non-zero number divided by itself equals 1.

• If $a + b = 0$, then the expression is undefined because division by zero is not allowed.

So, the result depends on the condition of $a + b$. If $a + b \neq 0$, the answer is 1. Otherwise, it's undefined.

Would you like more details, or do you have any questions?

Here are five related questions to explore:

1. What happens if $a + b = 0$ in a more complex expression?
2. How does the value of a fraction change when the numerator and denominator are equal?
3. What is the significance of division by zero in mathematics?
4. Can the simplification $\frac{x}{x} = 1$ always be applied?
5. How can we handle undefined expressions in mathematical proofs?

Tip: Always check for division by zero before simplifying an expression.