This is a free lesson from our course in Algebra I It explains how to identify mistakes in the order of operations in a multi-step derivation. Using examples, it explains that we have to follow the order of operations PEMDAS (Parenthesis, Exponents, Multiplication, Division, Addition, Subtraction). Simply put, when you have to simplify any expression, you should first perform any calculations inside parentheses, and then perform all multiplication and division operations working from left to right, and lastly perform all addition and subtraction from left to right. For example, when we solve the equation 3(x + 5) = 2x + 35.(More text below video...)
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(Continued from above) The steps to solve the above equation are:
� step 1    3x + 15 = 2x  + 35
� step 2    5x + 15 =  35
� step 3    5 = 20
� step 4     x = 4
If you look at the solution, the first incorrect step is step 2.
To avoid such situation order of operation is very important.
Rules:
� calculations must be done from left to right.
� calculations in brackets (parenthesis) are done first. When you have more than one set of brackets, do the inner brackets first.
� exponents (or radicals) must be done next.
� multiply and divide in the order the operations occur.
� add and subtract in the order the operations occur.
Must always do:
� simplify inside groupings of parentheses, brackets and braces first. Work with the innermost pair, moving outward.
� simplify the exponents.
� do the multiplication and division in order from left to right.
� do the addition and subtraction in order from left to right.
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