Please post any and all homework or other textbookstyle problems in one of the Homework & Coursework Questions...

Feb2313 09:24 AM
micromass

1 
30,537 
One of my books defines a relation which is "evidently" an equivalence relation. It says that two idempotents in a...

Feb2108 04:07 PM
cogitoČ

2 
1,685 
is there a direct proof that an idempotent matrix with inverse, can only be an identity matirx
i can't find about...

Feb1811 07:48 AM
thegreenlaser

2 
3,070 
If A and B are idempotent(A=A^2) and AB=BA, prove that AB is idempotent.
this is what i got so far.
AB=BA...

Oct1507 03:02 PM
learningphysics

9 
9,283 
How do you proove what the idempotents of the ring Z/100Z are?
I know by trial and error that they are the elements...

Apr1408 11:20 AM
quasar987

1 
1,089 
In the following 0/1 matrix I'm trying to identify every largest submatrices formed by 1's as shown in the picture. ...

Apr614 12:20 PM
Mark44

1 
276 
3.5036799918564934004113
I need help identifying this real number. The closest I have gotten is e+pi/4.
But I...

Dec912 11:53 PM
haruspex

9 
1,835 
Hi, everyone:
I have been playing around with tensor products of vector spaces recently.
This question came up:...

Dec2107 10:31 AM
mathwonk

4 
1,628 
The question is to prove for finite dimensional T: V to W,
T is injective iff there exists an S: W to V such that ST...

Mar409 04:16 AM
ThirstyDog

12 
3,543 
it is true in general that the sum (density of states for a physicst)
\sum_{n=0}^{\infty} \delta (x \gamma _{n}) ...

Dec1408 06:40 AM
rscosa

1 
1,733 
If TP conjecture is false and there're only a finite number of primes then..could we write the sum of the reciprocal...

Sep1606 01:21 PM
lokofer

0 
2,106 
I want to show that if 1 were a congruent number then there would be an integer solution to the equation x^4y^4=u^2...

Mar2011 09:03 AM
dodo

3 
1,215 
Hi, can anyone explain to me if a 3 x 4 matrix can have independent columns? How about independent rows?
Thanks!

Apr1310 05:52 PM
VeeEight

3 
699 
I think this is true but not sure how to prove it. Suppose that A and B are both totally unimodular matrices then is...

Nov1011 11:02 PM
hedgeway

0 
816 
if A is a tridiagonal Matrix , what does this mean ?
what does tridiagonal mean in matrix ?
what is the property...

Nov2212 11:40 AM
HallsofIvy

2 
857 
Theorem: If A is a nilpotent square matrix (that is for some natural number k>0, A^k =0) then (I + A) is an invertible...

Oct2507 03:45 PM
SiddharthM

11 
4,522 
Suppose it is known that A is singular. Then the system Ax=0 has infinitely many solutions by the Invertible Matrix...

Dec1512 01:09 PM
Bipolarity

4 
1,055 
Hi
I am arguing with a friend about the following:
He claims that if a mxn matrix A, m>=n has a reduced...

Sep2310 03:08 PM
arkajad

4 
1,534 
This is certainly an elementary question, so I would be all the more grateful for the answer. Given: A and B are two...

Feb2414 03:39 AM
nomadreid

2 
428 
well this is the question... if a,m and n are positive integers with m<n, then (a^(2^m)+1) is a divisor of...

Oct2809 12:22 AM
Petek

1 
1,115 
I'm not sure I've convinced myself here.
Take the L be the set of all linear transformations from V > V, where V...

Oct1408 05:03 PM
Pere Callahan

16 
1,260 
If AB is invertible, then A and B are invertible for square matrices A and B.
I am curious about the proof of the...

Sep2713 02:57 PM
Erland

14 
5,315 
I'm looking for help to this problem. Here is my attempt:
I being the identity matrix and B^(1) being B to the...

Oct2011 11:07 PM
sam0617

2 
1,656 
I am curious:
if f and g are (complex) orthogonal functions, are f* and g also orthogonal? (* denotes complex...

Sep2913 10:27 AM
economicsnerd

2 
552 
hi
if F is inner automorphism , what does this mean ?
I think that if
F : G to G
then
we can write F(x) as ...

Dec1612 04:55 PM
Maths Lover

2 
765 
this is how i set up the problem, am i thinking correctly? for all h belong H b,a belong to G where Ha and Hb are...

Nov107 06:48 AM
matt grime

11 
2,832 
> if n = x(mod 10x+1) n,x>0 (where = is symbol used in "congruence" not equality)
then, is there a way...

Apr512 04:58 AM
DonAntonio

1 
1,364 
If n*n matrix, can row space ever be equal to null space?
P.S.: this is NOT a homework question. It's a general...

Apr710 02:27 PM
Noxide

5 
2,599 
If like DTn,d = pochhammer(n,d)/d!
For the triangle number in any dimension is true
Then whats say a simple root...

Oct2112 12:06 AM
qpwimblik

0 
1,042 
Hi. I need to: prove the group (Zp*,x) has exactly one element of order 2. Here, p is prime and (Zp*,x) is the set {1,...

Nov2611 03:26 PM
micromass

3 
1,795 
I have just had linear algebra exam, and one of the questions was to prove or disprove (give a counterexample) that if...

Oct3006 10:33 AM
*best&sweetest*

2 
1,926 
If the ztransform of x is X(z), then what is the ztransform of x in terms of X(z) ?

Dec1208 12:31 PM
turin

4 
4,360 
If two matrices are similar, it can be proved that their determinants are equal. What about the converse? I don't...

Jul2413 07:56 PM
mathwonk

5 
1,137 
The book I am going through says this :
The below proposition is false for real inner product spaces. As an...

Dec2812 06:46 PM
chiro

3 
895 
I defined the angle \theta between x \in \mathbb{R}^k and y \in \mathbb{R}^k in the way that:
\theta = \cos...

Aug311 10:19 PM
zhentil

1 
1,116 
Ok so I have an assignment for my Calculas/Geometry class and I seem to have not paid the greatest attention in class...

Jan308 09:37 AM
Mtl

2 
1,382 
Is it true that if \sigma \in S_n is a cycle of length k \leq n, then \sigma^k = \varepsilon, where \varepsilon is the...

May2809 01:04 AM
matt grime

5 
1,312 
If x,y are (2,2) complex matrices such that log(xy)=log(x)+log(y) then x,y commute

Dec407 07:44 PM
Count Iblis

0 
2,439 
If we knew the prime number counting function \pi(x) then how could we recover the nth prime?..of course an easy...

May606 08:07 AM
roger

7 
1,762 
Im new to theese forums and kindof new to number theory because im only a junior in highschool. so is there any...

Dec504 02:25 AM
Gokul43201

3 
1,601 
Let R be a ring of characteristic m > 0, and let n be any
integer. Show that:
if 1 < gcd(n,m) < m, then n · 1R is...

Apr2707 03:05 PM
Data

1 
1,469 