What Do Parentheses Mean?
Date: 08/15/2002 at 23:52:45 From: Jeffrey Subject: Algebra Dear Dr. Math, I was working on some algebra questions and the problems had parentheses in them. I didn't know you had to multiply to find the answer. Can you help me find ways to figure out what the parentheses mean?
Date: 08/16/2002 at 14:00:05 From: Doctor Peterson Subject: Re: Algebra Hi, Jeffrey. I suppose you mean something like 2(3+4) = 2*7 = 14 [here "*" is the multiplication sign] or (x-1)(x-2) = 0 [here "x" is a variable, and the equation is true if x is either 1 or 2] In such cases, the parentheses themselves don't tell you to multiply; they just mean that what's inside is to be treated as a single value, as when you first add 3+4 to get 7 before doing anything to it. But when two things (other than two numbers) are placed side by side in an algebraic expression, that means they are multiplied: xy means the product of the variables x and y, while x(y+1) means the product of x and y+1. When you are working only with numbers, rather than variables, the only way you can put two things side by side is when one or both are in parentheses, since 12 has to mean twelve, not 1 times 2. So often the first time you see this notation for multiplication, it involves parentheses. Here is a brief discussion of what parentheses are for: Brackets http://mathforum.org/library/drmath/view/58445.html and here is a little more detail: Explaining Order of Operations http://mathforum.org/library/drmath/view/57199.html If you have any further questions, feel free to write back. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/ D
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