Answer: To simplify the expression (m + b)/(m - b) + (m - b)/(m + b) - (m ^ 2 + b ^ 2)/(m ^ 2 - b ^ 2), we can first find a common denominator for the first two fractions, which is (m - b)(m + b), and then add them together. This gives us ((m + b) ^ 2 + (m - b) ^ 2) / (m ^ 2 - b ^ 2). We can then subtract the third fraction by finding a common denominator of (m - b)(m + b), which gives us (m ^ 2 + b ^ 2 - (m ^ 2 + b ^ 2)) / (m ^ 2 - b ^ 2). This simplifies to 0, so the final answer is just ((m + b) ^ 2 + (m - b) ^ 2) / (m ^ 2 - b ^ 2).