Question 4821: When working equations with parenthesis, what is the rule for the "sign" in front of the parenthesis?
Example #1: 2x + 5x -3(4 + 3) = -21; will the plus sign inside of the parenthesis become a minus (negative) sign and the negative sign in front of the 3 outside of the parenthesis become a positive sign?
Example #2: 2x + 5x 3(4 - 3) = -21; will the minus (negative) sign inside of the parenthesis not change because of the 3 outside of the parenthesis is a
positive sign?
Thank You,
TSJ - AL
Found 2 solutions by longjonsilver, Abbey:
Answer by longjonsilver(2297)   (Show Source):
You can put this solution on YOUR website! hi, this is a classic problem area for students - basically because mathematicians are lazy and we miss out some notation, because we assume everybody knows this, but of course when you are learning maths, you do not know everything :-). So,
 is really  --> the 4 has a + sign in front of it too, because it is the number +4, but the software is being "clever" and not showing it, because it assumes everybody knows it is there!
So, for the bracket, we have the number -3 to be multiplied with both +4 and +3 within the bracket:
(-3)*(+4) is -12
(-3)*(+3) is -9
so, the equation becomes 2x + 5x -12 -9 = -21
We can now collect like terms together on the lefthand side: 7x - 19 = -21 which becomes 7x = -2 etc
As for  , again we have:
(+3)*(+4) is +12
(+3)*(-3) is -9
--> 
Hope this is clearer for you?
jon.
Answer by Abbey(339)  (Show Source):
You can put this solution on YOUR website! Think about the minus sign as being a negative attached to the number immediately following it. In the first example the negative is in front of the 3, so when you clear the parentheses, you will multiply -3 times what is inside (in this case it is seven)
If there is no number in front of the parentheses, it indicates the number one is in front, so you would multiply everything inside the parentheses by -1.
Example:
-3(4+3+x) = -3(7+x) = -21-3x
-3(4+3-x) = -3(7-x) = -21+3x
-(4+3+x) = -1(7+x) = -7-x
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