Summation Problems!

1. Sep 19, 2009

axellerate

My geography prof assigned these... believe it or not. Its a quiz and its worth 5% of our mark.

1) Σi^4 = 1^xi Variables - n=4 x1=1 x2=6 x3=9 x4=17 (i think its 4)

2) (Σi^4=1^xi)^2 n=4 x1=3 x2=10 x3=9 x4=12 (i think this one is 4 also)

3) Σi^2= 1Σj^2 = 1^xij n=2 m=2 x11=2 x12=12 x21=4 x22=17 (i havent the faintest idea...)

4) Σi^3= 1 xi/2 n=3 x1=3 x2=16 x3=6 (i think this one is 12.5)

5) Σi^n=1 xi/zi n=3 x1=14 x2=19 x3=16 z1=4 z2=9 z3=6
(i think the answer is apprx 8.28)

I have no idea why my geography teacher is giving us this quiz... i am not a math major. I have to round all answer to 2 decimal places if rounding is possible in the solution. I dont require the work as its an online quiz. But if u want to include it, all the better.

2. Sep 19, 2009

elduderino

please use latex typeset to represent such equations. its a pain to read them or get what the question is.

3. Sep 20, 2009

HallsofIvy

Staff Emeritus

Whether you are a math major or not, you should know enough arithmetic to at least understand what these are asking.
This makes no sense. Σi^4 would mean (1)^4+ (2)^4+ (3)^4+ ... but where do you stop? "n= 4" makes no sense because you did not write an "n" in your formula. If you mean "i runs from 1 to 4" then it is (1)^4+ (2)^4+ (3)^4+ (4)^4, then you just need to do the multiplications and the final addition. It's just arithmetic.

I can make no sense out of 1^xi at all. 1 to any positive power is just 1.

4. Oct 7, 2009

axellerate

HallsOfIvy,

My friend used my account to post this. Im currently a Medical Student, and I have never encountered the Summation (Σ) sign. Knowing arithmetic is one thing; but understanding what the equations mean is another. You must be taught what the variables / letters etc... mean. One cannot assume. The equations are written perfectly, and Σi^4 is a standardly used in summation problems. I suggest you do a little research before bashing one work. BTW: The n variable does stand for something. Why don't I let Mr.Arithmetic figure it out. I mean, you should know what it means... You should know enough arithmetic to understand the variables right?

Also, my buddy in forth year mech. engineering ended up solving each problem flawlessly with no issues.

The Guy that Doesn't understand arithmetic.

Axellerate

5. Oct 7, 2009

Staff: Mentor

axellerate,
Notwithstanding that you are a medical student, or that your friend posted it, the problems in the first post make no sense. For example, in the first one, Σi^4 = 1^xi, I know what the summation on the left side means, but don't see how it could possibly be equal to what's on the right side. And what do the variables have to do with this?

6. Oct 7, 2009

LCKurtz

I suggest that you, Mr. math illiterate future MD, don't need to show up here and tell posters that have probably forgotten more mathematics than you ever knew, that they need to "do a little research" because they can't make sense of a nonsense post.

7. Oct 8, 2009

"The equations are written perfectly,"
Not in the first post - they are garbled to the point of being crap.

"Also, my buddy in forth year mech. engineering ended up solving each problem flawlessly with no issues."
I'd be amazed at that, but possible. Look at the way the problems he saw, and compare to what was posted here. How dissimilar in appearance are they?

"One cannot assume. The equations are written perfectly, and Σi^4 is a standardly used in summation problems. I suggest you do a little research before bashing one work. BTW: The n variable does stand for something. Why don't I let Mr.Arithmetic figure it out. I mean, you should know what it means... You should know enough arithmetic to understand the variables right?"

Neither HallsofIvy nor Mark44 made an assumption; both stated facts. You seem to be the one making the assumption: if you are unfamiliar with the mathematics, as you yourself claimed, it is not possible for you to know that that equations are correct. You also assumed that these two do not know what they are doing - another assumption, equally as false as the first.

I'll take you at your word that you are a medical student - and state given your apparent arrogant attitude, you are going to suck at being a doctor. Assumption or prophecy? I don't know.