Tutoring high school math, scientific calculators are a permanent fascination. The tutor mentions a quirk many might share.

Due to

and the fact that a common exponent notation is

x^a=x^a,

it follows that

(-8)^(2/3)=4.

Curiously, of all the calculators in front of me this moment, only two – the Casio fx-991ES PLUS C and the TI-83 Plus (a graphing calculator) – are willing to perform (-8)^(2/3) as presented. The others give “ERROR”.

Yet, invoking the rule shown above, we can rewrite the calculation as

³√(-8)²

Then, all the scientific calculators I have at hand will give the answer 4. However, the calculator aboard my mobile phone will only do so if the square is posed before the cube root.

HTH:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC