In English we use the word combination loosely without thinking if the order of things is important. Finally working from left to right. My fruit salad is a combination of apples grapes and bananas We dont care what order the fruits are in they could also be bananas grapes and apples or grapes apples and bananas its the same fruit salad.
The deal is that theres a specific process you need to follow when taking terms out of parentheses and what you do hinges on whether theres a positive sign or a negative sign in front of the parentheses.
Parentheses are used to group numbers or variables or both. Anything in parentheses must be simplified first Exponents. To separate numbers for clarity to indicate multiplication and to group numbers together. Combinations and Permutations Whats the Difference.