negative number raised to even power

[Joe Horn]

(04-25-2015 11:24 AM)DrD Wrote:  A few TI calcs, and my hp50g agree with the way I learned, though, that -2^2 = 4.

In RPN... but that's because you're negating first, then squaring, which is NOT what -2^2 means. Proof: type -2^2 into the EquationWriter (or inside single quote marks, or in algebraic mode) and evaluate it. You'll get -4, because the power is performed first, then the negation, by standard "order of operations".

Try both -2^2 and (-2)^2 on Prime, in Home, with Textbook Display turned off (that's different from Textbook Entry!), and look at the history. It makes it evident what's happening.

Quote:"don't forget to enclose negative numbers in parentheses when raising to even powers!"

Not only even powers. ANY non-odd power (e.g. -2^pi or -2^i) needs parentheses if you want to perform the negation before the power.