aspiecat

05-23-2014, 02:13 PM

I was marking DS's Geometry today, including, in accordance with how things are done in Math U See, a systematic review of previously-taught material from Algebra I. This is done in every practice lesson to ensure kids don't forget what they have learned previously. Fair enough - I think it's a good idea.

One of the questions asked was the following:

-3^2 = ?

There were three other questions that were similar, but there were parentheses involved in different places, eg, -(12)^2 = ? These questions were obviously checking that the student still knows that parentheses or lack thereof can change how something with an exponent is worked out.

Now, I was taught as a kid that -3 squared is positive 9, but apparently the way kids are taught nowadays is that what they are doing is negating the 3 squared - so the answer is actually -9.

Therefore:

-3^2 = - (3)(3) = -9

I discussed this at length with my DH and FIL, both who agreed with me that -3 ^2 = 9, however, after a while, we decided that what is happening is kids are increasingly being taught and retaught as if they are dumber than hell. Sure, we could see HOW -3^2 is actually interpreted as the negating of -3^2, and the only way to get positive 9 out of this is to have (-3)^2.

(-3)^2 = (-3)(-3) = 9

I clearly remember the concept *I* was taught as -3^2 meant -3 x -3, which equals positive 9. But it was in context, when working something out, definitely NOT a standalone concept that had no relationship to anything else.

After some heated debate, we came to the conclusion that many PS teachers are being taught so simplistically, and they in turn teach kids simplistically. Hence, textbooks are often carrying on this simplistic, "let's assume our kids can't be taught things in context" manner.

While the rules of Order of Operations might well hold firm and true here, we all three of us were shocked that any concept is being taught out of context. It's as if society expects to turn out kids who can't think properly.

Aspie

One of the questions asked was the following:

-3^2 = ?

There were three other questions that were similar, but there were parentheses involved in different places, eg, -(12)^2 = ? These questions were obviously checking that the student still knows that parentheses or lack thereof can change how something with an exponent is worked out.

Now, I was taught as a kid that -3 squared is positive 9, but apparently the way kids are taught nowadays is that what they are doing is negating the 3 squared - so the answer is actually -9.

Therefore:

-3^2 = - (3)(3) = -9

I discussed this at length with my DH and FIL, both who agreed with me that -3 ^2 = 9, however, after a while, we decided that what is happening is kids are increasingly being taught and retaught as if they are dumber than hell. Sure, we could see HOW -3^2 is actually interpreted as the negating of -3^2, and the only way to get positive 9 out of this is to have (-3)^2.

(-3)^2 = (-3)(-3) = 9

I clearly remember the concept *I* was taught as -3^2 meant -3 x -3, which equals positive 9. But it was in context, when working something out, definitely NOT a standalone concept that had no relationship to anything else.

After some heated debate, we came to the conclusion that many PS teachers are being taught so simplistically, and they in turn teach kids simplistically. Hence, textbooks are often carrying on this simplistic, "let's assume our kids can't be taught things in context" manner.

While the rules of Order of Operations might well hold firm and true here, we all three of us were shocked that any concept is being taught out of context. It's as if society expects to turn out kids who can't think properly.

Aspie