I am a simple man who bows to your superior knowledge. At least all my
maths teachers are dead now :-)

Cheers,
Ken Russell


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"Atreides" <atreides1AThotmailD0Tcom wrote in message
...
Doesn't -(x^2) satisfy -9?

Yes, according to your convention, you would have to write -(x^2). So
consider the two systems we could have:

1. x^2 the opposite of which is -x^2
2. x^2 the opposite of which is -(x^2)

System number one (which, in my experience, is standard in maths, science
and engineering textbooks) makes more sense to me. Indices or powers have
precedence over multiplication.

Consider graphs of parabolas. According to your definition, the graphs:

y = x^2

AND

y = -x^2

would be the same graph. However, in my experience, eveyone knows that y =
x^2 is a "U" shape while y = -x^2 is an "upsidedown-U" shape.

Would you agree?

Cheers,
Peter





"Ken Russell" wrote:


--
Ken Russell


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"Atreides" <atreides1AThotmailD0Tcom wrote in message
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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


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"Atreides" <atreides1AThotmailD0Tcom wrote in message
...
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