1. Let's understand how signs change in algebraic expressions. 2. When you multiply or divide by a negative number, the sign of the term changes: a positive becomes negative, and a negative becomes positive. 3. For example, multiplying $-3$ by $-1$ gives $+3$, and multiplying $+4$ by $-1$ gives $-4$. 4. Another common case is when you distribute a negative sign across parentheses: $-(a + b) = -a - b$. 5. This happens because the negative sign outside the parentheses multiplies each term inside. 6. So, changing signs is about multiplication by $-1$ or distributing negatives. 7. Remember, adding a negative is the same as subtracting, and subtracting a negative is the same as adding. 8. For example, $5 - (-2) = 5 + 2 = 7$. 9. Understanding these rules helps you correctly change signs in expressions.