Question about one specific Math question!! June 06

Test Preparation SAT Preparation
1

<p>it's about the one that said
x^2+y^2+z^2=9, then it asked what is the value of x+y+z</p>

<p>In the discussion thread most of you said 5 because: 2^2+2^2+1^2=9</p>

<p>HOWEVER....</p>

<p>what is preventing the numbers from being</p>

<p>3^2+0^2+0^2=9 so then the answer would be 3
OR
2^2+-2^2+1^2=9 so the answer would be 1</p>

<p>or any other combo of negative numbers and such.</p>

<p>So the question I want to know is if any of you remember the limitations they gave us on that problem.</p>

<p>Also, which math was experimental (east coast) like some of the problems in that section b/c I can't remember which questions were in which section please.
thanks : )</p>

2

<p>I think they specified positive intergers...meaning 0 and -2 couldn't be used?</p>

3

<p>i got 3 but everyone keeps telling me i was wrong so i dunno</p>

4

<p>Very easy. Simplify both sides of the equation. Square root both sides and you get: x+y+z=3. SO the answer is 3</p>

5

<p>i wanna bummp this 2 see what other ppl have 2 say</p>

6

<p>could anyone post the complete question? It'll be good practice</p>

7

<p>Sqrt( x^2 + y^2 + z^2) is not x + y + z .</p>

8

<p>it was something like if X^2+y^2+z^2=9 what does x+y+z=?</p>

9

<p>5...clearly</p>

<p>unless you could use negative #s or 0</p>

10

<p>does anyone know where you could use negative numbers?</p>

11

<p>*whether....</p>

12

<p>in this case, I'm positive that the limitation would HAVE to be positive integers, unless if was one of those "what is one possible value" questions.</p>

13

<p>sorry, what I said didn't make sense... usually I don't think they would limit exclusively to negative numbers and 0 so...</p>

14

<p>sqrt(x^2+y^2+z^2) is NOT x+y+z</p>

<p>That is one of the unforgiveable sins of algebra.</p>

15

<p>AHH!! No one has been able to answer my question! : (</p>

16

<p>I think that the problem is wrong or one other important thing is missing.</p>

<p>Since (x+y+z)^2= x^2 + y^2 + z^2 + 2xy + 2xz + 2yz,
I think at least the value of xy + yz + xz should have been given.</p>

17

<p>hmm...are we allowed to ask the college board about a question?</p>

18

<p>yea thats a good question</p>

19

<p>I'm pretty sure it specified positive integers on the test... or else I would have noticed the different answers</p>

20

<p>Positive integers it was.</p>