Gifted Issues Discussion homepage Forums General Discussion Gonna be a long year

Hmm. If she had meant, "Use the distributive property to simplify," I would be inclined to agree. But she wrote:


If this comment has been conveyed accurately, the expression would be:

3(99)-5, as it wants you to subtract one from A. This would give 292, not 295.

Again, my brain isn't functioning at full capacity right now; am I wrong? If I am wrong, I will stop contributing to this thread.

Well... my math teachers wanted things written in simplest form, so they would have wanted this equation written with n instead of n-1. It may seem silly at this level of math, but it gets to be helpful as you move into more complicated equations.

Did the teacher take points off for it or just point out that it wasn't in simplest form? And did the instructions ask for it in simplest form? (you don't have to actually answer those questions - just pointing out that this example doesn't sound like an issue that I'd lose any sleep over).

Best wishes,

polarbear

No, she wants the A-sub-n-minus-1 in the equation, which seems to let out the simplification of the thing he wrote -- I think. We're going to work out a plea for clarification in suitable diplomatic form and see what falls out.

I am trying to teach the boy diplomacy, so this class may at least be good for that.

Well, it is correct to write this series as

An = 3n - 5

or

An = An-1 + 3; A1 = -2

The statement that An = 3 An-1 - 5 is just wrong. If that were correct, then given that we know that A1 = -2, then A2 would be 3(-2) - 5 = -11, and A3 would be 3(-11) - 5 = -38, etc.

Good deal -- we'll see if we can get a clarification from her, and see if she meant anything like that. I hope so, for the sake of the class.

So far they've only been dealing with n-1 and A-sub-n-minus-1 constructions, so I'm pretty sure she wasn't thinking of the 3n-5. If so, then she's thinking ahead of where they are and that would be a good thing, too!