When adding brackets, if there is a plus sign or a multiplication sign in front of the brackets, the symbols of the items in the brackets remain unchanged. If the parentheses are preceded by a minus sign or a division sign, everything in the parentheses will change sign. Parentheses are the other way around. If there is a minus sign before the parentheses, everything in it will change, but the plus sign will remain the same.
The rule of removing brackets is based on the distribution law of multiplication. That is, when the factor outside the bracket is the municipal number, the bullet after removing the bracket is opposite to the symbol in the original bracket. When the factor outside the bracket is negative, the symbol after the bracket is opposite to the symbol inside the bracket.
Extended data:
1. If there is a plus sign or a multiplication sign in front of the parentheses, the symbols in the parentheses will remain unchanged after the parentheses are added.
2. If there is a minus sign or a division sign in front of the bracket, all the symbols in the bracket will become opposite symbols after adding the bracket.
3. Adding parentheses can be tested by deleting parentheses. When adding parentheses, if there is a plus sign or a multiplication sign before parentheses, all items in parentheses remain unchanged; If. Parentheses are preceded by a minus sign or a division sign, and everything in parentheses changes sign. For example; 1 . a+b+ c = a+(b+ c)； 2.a-b-c=a-(b+c) Rules for removing brackets 1 When the plus sign comes before the brackets, the brackets are removed, and the formula in the brackets remains unchanged.