Unary minus precedence preference

[Claudio L.]

(07-23-2014 07:59 PM)Wes Loewer Wrote:  My point is simply that it really boils down to convention. Never-the-less, I'm going to use your example in class next time as a way of convincing students that the standard convention makes sense. :-)

You should do a poll, and ask the class what's the result of the following expressions:
4-2^2= (I bet 100% of the students will say it's zero)
-2^2 + 4 = (I think 100% of them will say it's zero as well).
I think if you show first 4-2^2=0, 100% will see the similarity of the expressions written on the board and will immediately agree on the zero result of the second one.
Now try reversing the order (to a different group of students):
-2^2+4 = goes first (I think some students will say 0 and some will say 8)
4-2^2 = (100% will agree it's zero)

I think only in the second group, when you show the ambiguous one first (by itself), the confusion will appear.

Sorry, now we are doing social experiments but would be interesting to know how students perceive the formula just by looking at it.
Claudio