When judging whether several terms in a polynomial are similar:
(1) contains the same letters.
(2) The subscripts of the same letters are equal respectively.
At the same time also need to pay attention to two points:
(1) Similar terms have nothing to do with coefficients or alphabetical order;
(2) There are not necessarily two similar items, but there may be three, four, ..., but at least two.
Extended data
When merging similar items, the same types are put together in parentheses. After the merger, we must pay attention to two points:
(1) When there is a "+"in front of the bracket, remove the bracket and the "+"in front of it, and the symbols of the items in the bracket remain unchanged;
(2) When there is a "one" in front of the bracket, remove the bracket and the "one" in front and change all the symbols in the bracket.
Example: remove the brackets and merge the similar terms in the following polynomials;
A+(3b-5a)-(a-2b)
[Reminder] Before removing brackets, observe the symbols before brackets, and then consider whether the symbols of the items in the original brackets have changed after removing brackets.
Original formula =a+3b-5a-a+2b= 5a+5b.
Of course, when adding and subtracting several algebraic expressions, each algebraic expression is usually enclosed in brackets, then connected with the addition and subtraction signs, and then the brackets are removed to merge similar items.
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