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TargetMBA007
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14 Jan 2020, 20:07
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Hi Guys.
Here is a quick calculation, which I know is incorrect as the answer is negative 5/3. However, I was just curious, as to which math rule is being broken here? -4 has been factored out and then divided by 0. As 0 divided by any number would always be 0, should this not eliminate the negative sign?
Screenshot_3.png [ 158.95 KiB | Viewed 3830 times ]
Thanks
Here is a quick calculation, which I know is incorrect as the answer is negative 5/3. However, I was just curious, as to which math rule is being broken here? -4 has been factored out and then divided by 0. As 0 divided by any number would always be 0, should this not eliminate the negative sign?
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Screenshot_3.png [ 158.95 KiB | Viewed 3830 times ]
Thanks
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15 Jan 2020, 04:47
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TargetMBA007
First of all you cannot divide any number by 0 but you have taken -12/0, so I believe it should be just -12 or -12/1.
Now in your calculations -4(3x+5)=0.....3x+5=0/(-4)=0.....3x=-5....x=-5/3
31 Jan 2020, 18:36
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TargetMBA007
You've made three different math mistakes in this calculation!
First, there's one that you already noticed yourself. It's in this line:
-4(3x + 5) = 0
3x = 5
You skipped a step there, and that's where the error happened. A good rule of thumb is to stay aware of what math operation you're actually doing (adding? subtracting? multiplying? etc) at each step, and to only do one math operation in each step.
If you have -4(3x + 5) = 0, then the first step is to divide both sides by -4.
-4(3x + 5) = 0
3x + 5 = 0/(-4) = 0
(You're correct that dividing zero by -4 just comes out to 0. No need to worry about the negative.)
Now you have 3x + 5 = 0. The next step is to subtract 5 from both sides:
3x + 5 - 5 = 0 - 5
3x = -5
So, you want to end up with 3x = -5, not 3x = 5.
----
One other mistake is that you can't start out with 12/0 in your original equation. Since 12/0 is undefined, the equation you've written will never be true - that is, there will never be a value of x that makes everything come out correctly, since you'll always have that 'undefined' term on the left side. There's no value of x that'll fix it!
----
Finally, it looks like you turned the 12/0 into 12(x + 2)/(x + 2) when you went from the first line to the second. It's fine to multiply the top and bottom of a fraction by the same value. For instance, this would be fine:
7/3
= 7(x + 1)/3(x + 1)
But if you try to multiply the top and bottom of 12/0 by x + 2, then you actually end up getting 12(x+2) / 0. That's because 0 times anything (even with a variable in it) is still just 0. 12(x+2) / (x + 2) is actually equal to 12/1, not 12/0.
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
