The expression $\sqrt{1 + (a+b)^2}$ cannot be simplified further using elementary algebraic techniques. The expression inside the square root, $1 + (a+b)^2$, does not have a factorization that would allow the square root to be expressed in a simpler form.

However, depending on the context, some approximations or special cases could be considered:

1. If $a + b$ is small: If $(a + b)$ is much smaller than 1, a first-order Taylor expansion around $a+b = 0$ can give: $\sqrt{1 + (a+b)^2} \approx 1 + \frac{(a+b)^2}{2}$ This is an approximation that may be useful in certain cases.

2. If $a + b$ is zero: The expression simplifies to $\sqrt{1} = 1$.

Without additional context, the expression $\sqrt{1 + (a+b)^2}$ is already in its simplest form.

Would you like more information or have any questions? Here are some related topics you might find interesting:

1. How can you use the binomial approximation for simplifying square roots?
2. What are Taylor series, and how are they used to approximate functions?
3. What are the special cases where $\sqrt{1 + x^2}$ simplifies easily?
4. How does the expression $\sqrt{1 + x^2}$ relate to hyperbolic trigonometric functions?
5. What are some techniques for simplifying square roots in algebraic expressions?
6. Can you express $\sqrt{1 + (a+b)^2}$ using hyperbolic functions?
7. How does the expression $\sqrt{1 + (a+b)^2}$ arise in physics or geometry?
8. What are some practical applications of square root expressions in engineering?

Tip: When simplifying expressions, always check for special cases and approximations that might apply to the problem at hand.