Gabe G.

asked • 09/29/21

Simplify 8/2(2+2)

I am engaged in an argument with an educated individual who claims that under no circumstances may you assume that 8/4x = 2x due to the fact that 2x = x2 and is “its own thing”. However, my understanding of monomials is such that their numerical aspect may be divided or multiplied when obligated by PEMDAS. I believe that our disagreement stems from the unfortunate complications that arise when vertical fractions are converted to horizontal fractions without proper indication of the bounds of the numerator and denominator. He assumes that the bounds of the denominator in the equation in the Title extend to the end of the equation. However, I am nearly certain that this is an incorrect assumption, as my mathematical upbringing has led me to believe, and I understand that once the operation inside the parentheses is completed, division and multiplication are performed left to right. As such, the equation simplifies to 8/2(4), which simplifies to 4(4), which = 16.


Additionally, he supplied an example from a textbook where they had written “mx/bx = m/b”. In this example, the textbook authors want readers to assume that there are parentheses defining the bounds of the numerator and denominator. However, simplifying this equation according to PEMDAS yields m * x/b * x = mx^2/b. This is technically an error by the textbook authors, yes?

1 Expert Answer

By:

Raymond B. answered • 10/05/21

Tutor
5 (2)

Math, microeconomics or criminal justice

Gabe G.

Thank you for your response! With all due respect, I was under the impression that multiplication and division were given the same priority under the order of operations (i.e. PEMDAS could just as correctly be written as PEDMAS). When both multiplication and division are present, they are executed from left to right. Excerpt from (https://math.berkeley.edu/~gbergman/misc/numbers/ord_ops.html) “Teachers explain that it means "Parentheses — then Exponents — then Multiplication and Division — then Addition and Subtraction", with the proviso that in the "Addition and Subtraction" step, and likewise in the "Multiplication and Division" step, one calculates from left to right” This source also explains rather well the original question I had. a/b(c) is an ambiguous notation with no correct answer unless parentheses are supplied. Assuming either answer is both correct and incorrect until disambiguated. Therefore, mx/bx is ambiguous since it neither specifies m(x/b)x or (mx)/(bx). However, it can be (most likely correctly) surmised that the textbook authors intended it to be solved by cancelling out factors. Thank you again for your response!
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10/05/21

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