Problem 183

To prove a mathematical proposition using the method of contradiction, we negate the conclusion we aim to prove, obtaining the negation of the conclusion.

The negation of the proposition "If $x^2-1=0$, then $x=-1$ or $x=1$" is: "If $x^2-1=0$, then $x \neq -1$ and $x \neq 1$".

Therefore, the answer is: "If $x^2-1=0$, then $x \neq -1$ and $x \neq 1$".

According to the definition of the negation of a proposition, the negation of "If $x^2-1=0$, then $x=-1$ or $x=1$" is obtained, which is what we seek.

This question mainly examines the method and steps of proving a mathematical proposition using the negation of the proposition and the method of contradiction. Negating the conclusion to be proved and obtaining the opposite of the conclusion to be proved is the breakthrough in solving the problem, and it is considered a medium-level question.

$\boxed{\text{If } x^2-1=0, \text{ then } x \neq -1 \text{ and } x \neq 1}$.