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2[9-12]/[-5]+[5]

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Michael J. | Calculus Tutor with a Physics DegreeCalculus Tutor with a Physics Degree
4.9 4.9 (15 lesson ratings) (15)
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According to order of operations, we evaluate expressions inside parenthesis (and brackets) first, then evaluate exponents, then multiplication AND division left to right, then addition AND subtraction left to right.
 
Then, the steps, as written, would be:
[9-12] = -3
 
Rewrite:
2*[-3]/[-5] + 5
 
[-6]/[-5] + 5
 
A negative divided by a negative results in a positive, thus:
6/5 + 5
Now we need a common denominator.  The least common denominator (LCD) is 5.  The number 5, expressed as a fraction, is 5/1.  Thus, we must multiply this term by [5]/[5] to get [25]/[5]
 
Now adding:
 
6/[5] + [25]/[5] = [6 + 25]/[-5] = [31]/[5]
 
 
Now, looking at the problem, I wonder if you didn't mean
2[9-12]/[[-5]+5]
 
In which case we must evaluate the denominator: -5 + 5 = 0
Division by 0 is undefined.