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Just went through this with an online questioner        When you enter   -9 and then square it , the calculator gives you   - (9^2)    instead of  (-9)^2

I feel this is an error, though it shows ABOVE the calculator what it is going to do, I've not seen other calculators do it this way....  Back when I was in Engineering school, slide rules would never do this....ha      I wonder how many people even KNOW what a slide rule is (was) !

Thanx    ~jc

Guest Nov 21, 2015

Best Answer 

 #18
avatar+91001 
+5

jc and Hayley,  

Why don't you both join up?

It is better here if you are a proper part of the community.  It is free and easy.   laugh

Melody  Nov 21, 2015
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22+0 Answers

 #1
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When you square -9, remember to press the = key to give you 81.

Guest Nov 21, 2015
 #2
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Nope....when you do that it gives you -81

Guest Nov 21, 2015
 #3
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Tbh, ive been getting 81 too, stupid calculators!! ive been getting very confused! Ugh! >:(

Guest Nov 21, 2015
 #4
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No the web2 calc is correct.

If it did it your way then

10 - 3^2 would equal 10 +9  which is obviously nonesense.

Melody  Nov 21, 2015
 #5
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I disagree Melody.   When I enter  '9'  then push the +- key and then square it it SHOULD give (-9)^2  NOT -(9^2).

Guest Nov 21, 2015
 #6
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+5

-9 is interpreted correctly as -1×9

-9^2= -1×9^2 = -1×81 = -81

 

However

(-9)^2=(-1×9)×(-1×9)=+81

Melody  Nov 21, 2015
edited by Melody  Nov 21, 2015
 #7
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I disagree Melody.   When I enter  '9'  then push the +- key and then square it it SHOULD give (-9)^2  NOT -(9^2).

Do you see the suttle, but real difference?

 

I'm not trying to SUBTRACT a square, I'm trying to get a square of a NEGATIVE

Guest Nov 21, 2015
 #8
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ooops   'subtle'

Guest Nov 21, 2015
 #9
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are you talking about my problem: 1x^2-9x+8=0?

This problem was such a tricky one!

Guest Nov 21, 2015
 #10
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Yes, we're talking about your problem.

 

Melody, I cannot find any calculator in my house or phone that does this this way....I understand what you are saying, but I think the calculator has a weird syntax glitch in this instance

 

When I want to find the SQUARE of NEGATIVE 9    I should be able to enter the following keys  '9'  ' +-'  and then the x^2 key to get 81    not -81       Currently to get the correct answer you have to enter (   9  +-  )  then the x^2 key...I under stand how to do it on this calculator, but other calculators do not do it in this manner......and it led one of our students to get an incorrect answer using the quadratic equation to solve the equation she mentions above....

Guest Nov 21, 2015
 #11
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+5

No I am not talking about your quadratic problem lol.

Maybe the other guy is. :)

 

Different calcs work differently I do not know of any standardized meaning of what +/- means.

If someone uses a tool in a test it is up to them to understand the nuances of the tool. Tell your student this and tell him to use (-9)^2.  That has a specifically defined meaning.

Melody  Nov 21, 2015
 #12
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Hello! My name is Hayley, and I am the student that was so confused. I kinda understand what your sayin'.

Guest Nov 21, 2015
 #13
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Agreed,   that is what we did    ...and I explained it to them.    ...and I WAS referring to her quadratic equation problem...that is where we found what I will continue to call an 'anomoly'       ha!     Thanx 

Guest Nov 21, 2015
 #14
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Interesting.. thxss for the help though, Melody :)

Guest Nov 21, 2015
 #15
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Ok i can also see your point.

I might try it on other calcs when I get home.  If the web2 calc treats it differently from all the others I will send this thread to admin. :)

Melody  Nov 21, 2015
 #16
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thank yoou! :)

-Hayley

Guest Nov 21, 2015
 #17
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I looked at a few different ONLINE calculators....seems a split between -81 and 81...I do not know what core engine the calculators are using though....in my random sample a few more said 81 and not -81  

I think it is like you said ...'know your tools and how to use them'    ....wise words

~jc

Guest Nov 21, 2015
 #18
avatar+91001 
+5
Best Answer

jc and Hayley,  

Why don't you both join up?

It is better here if you are a proper part of the community.  It is free and easy.   laugh

Melody  Nov 21, 2015
 #19
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0

I will one of these days, though I have enjoyed  'Shadow Guesting' for some time.  I wonder.... Is it easier to edit your answers as a member?  I often go back to add more info or fix a typo and I have to repost the whole thng.   How about 'pasting' ?    How about that annoying reCaptcha "i am not a robot" authenticity checker...does it go away?  (THAT would make it worthwhile!! ha)

~jc

Guest Nov 21, 2015
 #20
avatar+91001 
0

I will one of these days, though I have enjoyed  'Shadow Guesting' for some time.  I wonder.... Is it easier to edit your answers as a member?  I often go back to add more info or fix a typo and I have to repost the whole thng.   How about 'pasting' ?    How about that annoying reCaptcha "i am not a robot" authenticity checker...does it go away?  (THAT would make it worthwhile!! ha)

~jc

 

 

Hi jc                 (that is an edit,  LOL  )

I have only ever heard one member complain that she sometimes has trouble editing. I have NEVER had any trouble at all except with regards to LaTex.  Sometimes LaTex gets 'sticky'

I get the "I am not a robot " thing if I start a new thread but it NEVER comes up when I am just answering someone elses question.

 

We would like you to join.   laugh

Melody  Nov 21, 2015
edited by Melody  Nov 21, 2015
 #21
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"10 - 3^2 would equal 10 +9  which is obviously nonesense.'"

No, it wouldn't. There is no -3 in this, it's the equation 10-3. The 3^2 is executed first, then 10-9, giving 1.

I had the same problem with -1^0.5. The -1 is a number, to be powered with 0.5, giving i. -(1) or -(7) or -(x) should give a syntax error, because you need numbers on both sides for subtraction. Otherwise, there is no reason why it couldn't be -(1^0).5, giving -1.5. Nothing is before minus, the -1 is a single number, and should not be split. 0.5 is also a single number.

Guest Dec 3, 2016
 #22
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"-9 is interpreted correctly as -1×9

-9^2= -1×9^2 = -1×81 = -81"

30 is 3×10

30^2 = 3×10^2 = 3×100 = 300.

-1, 30, 0.5 — these are single numbers, and splitting them will break the order of operations. These "interpretations" should be used with brackets, but not the single numbers, there is no reason to bracket them.

Guest Dec 3, 2016

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