There is a "-"before the brackets. Remove the brackets and the "-"sign in front of them, and change the symbol of each item in brackets.
The basis of the parenthesis rule is actually the multiplicative distribution rate.
note:
Pay attention to the symbol before brackets, which is the basis for whether the items in brackets change their symbols after removing brackets.
When deleting brackets, the symbol before brackets should be deleted together with brackets.
It should be noted that when there is a "-"sign in front of the brackets, the symbols of the items in brackets will change after the brackets are removed. You can't just change the symbol of the first item or the first few items in brackets and forget to change other symbols.
If there is a numerical factor in front of the brackets, before removing the brackets, multiply the number with the items in brackets by multiplication and division to avoid mistakes.
When you encounter multiple brackets, you usually remove them from the inside out, or you can count the number of "-"from the outside in. Combining similar terms to combine similar terms in polynomials is called combining similar terms.
like
Clause).
Merging similar terms refers to putting forward the coefficients with the same algebraic terms and then calculating them.
When merging similar projects, the included letters and letter indexes remain unchanged.
The rules for merging similar projects are:
Add up the coefficients of similar items, and the result is taken as the coefficient, and the index of letters and letters remains unchanged.
Example 1: When 3x+5x+2x or ab+ab+ab, similar items can be merged.
3x+5x+2x=(3+5+2)x= 10x，a b+a b+ab =( 1+ 1+ 1)ab = 3ab
Example 2: (a+b) 2 = a 2+ab+ab+b 2
The step of merging two ab's is called merging similar items.
That is (a+b) 2 = a 2+2ab+b 2.