If the brackets in front are removed, it becomes10-2 ÷ (3+1) =10-2/4 =10-1/2 =19/2. If you remove the brackets. It became.
( 10-2)÷3+ 1=8÷3+ 1=(8/3)+ 1= 1 1/3; If you remove the two brackets, it becomes10-2 ÷ 3+1=1-2/3 = 31/3.
(a-b)×(c+d), for the same reason as above, neither bracket can be removed. A-b and c+d are enclosed in brackets, indicating that (a-b) is a whole, and (c+d) is also a whole, which is the multiplication or division of two whole.
However, if there is a+sign or a-sign between two brackets, the brackets can be removed; However, if it is a minus sign, after removing the brackets, the following figures should be changed.
(a-b)+(c+d)=a-b+c-d
(a-b)-(c+d)=a-b-c-d.(+d should become -d).
You got it?