Re: BIMDAS - Order of Calculation
From: Ken Russell (kenrussellmyhat_at_optushome.com.au)
Date: 02/22/05
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Date: Tue, 22 Feb 2005 18:04:09 +1100
Doesn't -(x^2) satisfy -9?
-- Ken Russell kenrussellyourhat@optushome.com.au Remove yourhat to reply by e-mail . "Atreides" <atreides1AThotmailD0Tcom> wrote in message news:26D8CA4A-B270-4F63-A7EB-1C1215CFF0CF@microsoft.com... > But then Ken, what reason would one have for writing: > > -x^2 > > if it really simplifies down to -x * -x = x^2? > > How would one write the opposite of the square of x? > > Cheers, > Peter > > > "Ken Russell" wrote: > >> -3^2 is the same as -3*-3 which equals 9 not -9 >> >> At least that's what I was taught over 60 years ago. >> >> -- >> Ken Russell >> >> kenrussellyourhat@optushome.com.au >> Remove yourhat to reply by e-mail >> .. >> >> "Atreides" <atreides1AThotmailD0Tcom> wrote in message >> news:C60BB320-A11E-4E81-87E3-52C3C407ED18@microsoft.com... >> > I've recently noticed that Excel flies in the face of standard >> > scientific, >> > mathematical and engineering convention in the calculation of powers >> > for >> > numbers that are then multiplied by a negative. >> > >> > The convention of mathematics, "BIMDAS" (or similar acronyms), states >> > that >> > _I_ndices (or powers, or exponents), should be calculated before >> > _M_ultiplication. Because of this, the following is accepted as >> > correct: >> > >> > -3^2 = -9. >> > >> > This is because it is the equivalent of (-1) * 3^2 = -1 * 9 = -9 >> > >> > However, Excel chooses to recognise this as (-3)^2 = 9. >> > >> > This error is particularly problematic when doing algebraic >> > computations >> > in >> > such a tool as Mathematica and then copying the result into Excel in >> > input >> > form. That is, >> > >> > -x^2 -> -A1^2 >> > -> -A1^2 >> > (Mathematica) (Mathematica with reference substituted) >> > (Excel) >> > >> > To correct the error, one must manually change it to: -(A1^2) >> > >> > QUESTIONS >> > 1: Why does Excel have this convention! >> > 2: Is there any way to change it/make is more convenient? >> > >> > I've only recently noticed this (which is quite scary to think how many >> > errors I may have made in the past!) >> > >> > Thanks for your time, >> > >> > Cheers, >> > Peter >> >> >>
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