I have a question about rearranging equations to solve for variables. What is the order of operations? Is it reversed? PEM DAS. When do I use SAD MEP. Can you give me a simple example of this or perhaps somewhere to practice this?

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- Mar 22nd 2011, 01:24 PMwizkid94Order of Operations
I have a question about rearranging equations to solve for variables. What is the order of operations? Is it reversed? PEM DAS. When do I use SAD MEP. Can you give me a simple example of this or perhaps somewhere to practice this?

- Mar 22nd 2011, 02:06 PMHallsofIvy
In a certain sense, yes. The point is that solving for x in some equation, we have get x alone on one side of the equation so we have "undo" whatever was done to x. And to "undo" we do the opposite (inverse) of every step

**and**in the opposite order. Think of it this way, to give someone a birthday present, you put the gift in a box, wrap the box in gift paper, then tie a ribbon around it. Once you have given the gift the person must do the opposite of each step- take the gift out of the box, remove the paper, untie the ribbon. Except, of course, you cannot take the gift out until after you have removed the paper and you cannot remove the paper until you have untied the ribbon- you must (1) untie the ribbon, (2) remove the paper, (3) remove the gift.

To calculate 3x+ 2 for some particular value of x, you would, by PEMDAS, first multiply 2 by x, then add 2. But to solve 3x+ 2= 4, you have to "undo" those, in the opposite order: First subtract 2,**then**divide by 3.