Excel is wrong in calculating -x^2
If you type in for example =-6^2, Excel gives you 36. This is incorrect. Excel is assuming you mean =(-6)^2. But -6^2 is different.
You can see this when you factorise. -6^2 = (-6)*(+6) = -36.
Whereas (-6)^2 = (-6)*(-6)=36.
Now if you type in = 0-6^2, only then does it give you the correct answer of -36.
This error goes against millennia of algebraic convention.
Plot the graph y=-x^2-7x-12 and then plot y=-7x-x^2-12. These two expressions are identical, yet Excel gives very different traces (the latter of the two gives the correct graph).
Another way to correct -x^2 would be to type =-(x^2) but you shouldn't have to. You don't write it out that way if you're plotting quadratics.
In the given example Excel is doing right.
Consider that a leading minus cannot be convertet to an operator (as it is in 0-6^2) becasue one of the operands is missing, so Excel interprets it as a part of the number. So "-6^2" becomes (-6)^(2) or "--6^2" becomes (-(-6))^(2) in this way no matter how much "-" you use you'll always get 36.
The correct way of getting -36 without using parenthesis is simply to type: -1*6^2
If you type the string "-6" into a cell you are pleased with the behaviour that it is convertet to the integer -6 rather than getting an "incomplete formula error", right?
Sergei Baklan commented
Actually second link shall be http://mathforum.org/library/drmath/view/69058.html
Sergei Baklan commented
That's a great question why people who designed Excel more than 30 years ago decided what negation is to be performed before exponentiation. But that's what they did, the order of Excel operations is described here https://support.office.com/en-gb/article/the-order-in-which-excel-performs-operations-in-formulas-28eaf0d7-7058-4eff-a8ea-0a835fafadb8. By the way, exactly the same logic is used for Google Sheets, it also returns +36 if type =-6^2.
That is almost 20-years old but quite interesting discussions about the subject on Math Forum https://support.office.com/en-gb/article/the-order-in-which-excel-performs-operations-in-formulas-28eaf0d7-7058-4eff-a8ea-0a835fafadb8.
I'm very suspicious what that will be ever changed. Same with year 1900 - someone who designed Excel decided what that is the leap year, which is not. That issue is also known for about 30 years, but it never will be corrected due to compatibility. There are only support articles which explain what we have what we have and have to live with that.