Recent content by tnutty

1. Diffy-Q question

Figured it out, thanks for looking.
2. Diffy-Q question

Homework Statement Consider the population model dP/dt = -P^2/50 + 2P for a species of fish in a lake. Suppose it is decided that fishing will be allowed, but it is unclear how many fishing licenses should be issued. Suppose the average catch of a fisherman with a license is 3 fish per...
3. Affine transformation proof

Oh, I should have read the question carefully. Thanks a lot.
4. Affine transformation proof

Homework Statement An affine transformation T : R^n --> R^m has the form T(x) = Ax + y, where x,y are vectors and A is an m x n matrix and y is in R^m. Show that T is not a linear transformation when b != 0. Homework Equations There are couple of useful definitions, but I think this one...
5. Boolean algebra

Make a truth table to see why. X can equal only 1 or 0 thus the truth table for x*x is below : -------- x x x*x 0 0 0 1 1 1 ------- As you see if X = 0, then X*X = 0 = X, and if X = 1, then X*X = 1 = X. Thus X*X = X
6. Basic Matrix Question

In the last row you have this : [0 0 0 0 1] which means this in equation form, 0X1 + 0X2 + 0X3 + 0X4 = 1, which means 0 = 1. This is impossible mathematically, right? Because a 0 cannot never equal 1, which means that the system is inconsistent, or no solution. So Yes you are correct as to...
7. Basic Matrix Question

Its ok, the problem is trying to make you think hard, but I think once you thought about the problem a little, you should then confirm it by solving the matrix.
8. Basic Matrix Question

well try to solve it out and see
9. Basic Matrix Question

Oh, wait see this : The original matrix : [3 -2 0 1 1] [1 2 -3 1 -1] [2 4 -6 2 0] realize that the last row is a multiple of row2. Lets scale the last row3 so we have : [3 -2 0 1 1] [1 2 -3 1 -1] [1 2 -3 1 0] Notice something there?
10. Basic Matrix Question

Oh wait, there are 3 equation, and 4 variables. Do you think we have enough information to solve this matrix?
11. Basic Matrix Question

The key thing is on row3.
12. Quick question about matrix operations.

Ok, I will search for it. Thanks.
13. Quick question about matrix operations.

>>"What I have done is replace the 2nd equation by itself + 1 times the first equation." See thats the part thats bugging me. From middle school I have took that method as granted. Do you think that there if a formal proof of why that method would work? Or is it just drawn from intuitive reason...
14. Quick question about matrix operations.

Say there are these systems of equations : x - 2y + z = 0 2y - 8z = 8 -4x + 5y + 9z = -9 In matrix form, it can be represented like this : -- [1 -2 1 0] < -- row 1 [0 2 -8 8] < -- row 2 [-4 5 9 -9] < -- row 3 When we do elementary row operations, say on row3 = row3 +...
15. Findin largest volume

A*z = 2z(xy+xz+yz) V = xyz x = V/yz P/4 = x+y+z P/4 - x - y = z A*z = 2z(xy+xz+yz) A( P/4 - x - y ) = 2(P/4 - x -y) ( V/z + V/y + yz ) is that right? For a rectangular box, we could compute the area of one size and multiply by its depth to get the volume no? I am...