# Search results

1. ### Linear Algebra - Linear transformations

Ok, I think I understand. so that is linear because L(2,3,5) = (0,0). And L(ku) = kL(u) = (0,0). But for b), the second part doesn't hold up because L(ku) = (1,2,-1) but kL(u) = k(1,2,-1) and they are not equal for all k. and c probably shows something similar. I will have to write it out...
2. ### Linear Algebra - Linear transformations

I guess my problem is, I don't know how to apply that to L(x,y,z) = (0,0). If it was L(v) = Av I would understand. I just don't understand the transformations themselves and how to apply them.
3. ### Linear Algebra - Linear transformations

Homework Statement which of the following are linear transformations. a) L(x,y,z) = (0,0) b) L(x,y,z) = (1 ,2, -1) c) L(x,y,z) = (x^2 + y, y - z) The Attempt at a Solution I know that L is a linear transformation if L(u + v) = L(u) + L(v) and L(ku) = kL(u). I am not sure how to...
4. ### Prove: A 2x2 matrix is nonsingular if and only if the determinant != 0

I probably should have mentioned. I don't have the definition of the determinant to work with. the problem actually says Show that the 2 x 2 matrix A is nonsingular if and only if ad-bc != 0. I've figured out the If matrix A is nonsingular, then ab-bc != 0 side. I just need the if ad - bc !=...
5. ### Prove: A 2x2 matrix is nonsingular if and only if the determinant != 0

Ok, but where does this come from?
6. ### Prove: A 2x2 matrix is nonsingular if and only if the determinant != 0

Homework Statement Prove: A 2x2 matrix is nonsingular if and only if the determinant != 0 The Attempt at a Solution I need to prove this, using logic and maybe the theorem that a n x n matrix is nonsingular if and only if it is row equivalent to I_n. I could use a push in the...
7. ### Linear transformation matrix

Homework Statement Let L: R^3 -> R^3 be a linear transformation such that L(i) = [1 2 -1], L(j) = [1 0 2] and L(k) = [1 1 3]. Find L([ 2 -1 3)]. All the numbers in [ ] should be vertical, but I don't know how to set that up. Homework Equations The Attempt at a Solution...
8. ### Two-variable calculus

Ah, I ge tit now, thanks
9. ### Two-variable calculus

I know how to take partial derivatives and directional derivatives...
10. ### Two-variable calculus

I'm not really sure how to go about that
11. ### Two-variable calculus

Homework Statement Show that the following limit does not exist: lim (x,y) --> (0,0) of x^2 / (y^2 + x^2) Homework Equations The Attempt at a Solution I think it involves using l'hospitals rule and using partial derivatives, but I really don't know.
12. ### Finding a power series representation

Homework Statement Start with the power series representation 1/(1-x) = sum from n=0 to inf. of x^n for abs(x) < 1 to find a power series representation for f(x) and determine the radius of convergence. f(x)=ln(5+x^2) Homework Equations The Attempt at a Solution Okay, so I...
13. ### Using root test and ratio test for divergence

Homework Statement Does this series converge or diverge? Series from n=1 to infinity n(-3)^(n+1) / 4^(n-1) Homework Equations The Attempt at a Solution Okay, I've tried it both ways. Ratio test: lim n --> inf. ((n+1)*(-3)^(n+1)/4^n) / (n * (-3)^n / 4^(n-1)) Now...
14. ### Testing for divergence

alright. So root test gives me limit of 2^1/n / 10. I don't know what 2 ^1/n goes to. Is that even possible?
15. ### Testing for divergence

It's (1+sin(n)). Hrm, smaller than 2. So I can compare it to 1/5^n. Now, I need to figure out how to prove that series converges. Is it a geometric series? Actually, I know it converges, based on the root test. But I don't think we can use the root test now.
16. ### Testing for divergence

Well, the top part diverges, the bottom causes it to go to 0. So I don't know what happens faster. Either it converges to 0, or it diverges. The solution must involve the comparison test or the limit comparison test. But I'm not sure what to compare it to.
17. ### Testing for divergence

Homework Statement Does the sum of the series from n=1 to infinity of 1+sin(n)/10^n converge or diverge. Homework Equations The Attempt at a Solution I can use the comparison test or the limit comparison test. I'm not sure where to go from here.
18. ### Implicit derivation

the equation x sin (xy) +2x² defines y implicitly as a function of x. assuming the derivative y' exists, show that it satisfies the equation y'x² cos (xy) +xy cos(xy)+sin (xy)+4x = 0. Help needed please. I found the derivative of the first equation is: sin xy + xy cos xy +4x. It's close...
19. ### Chain rule

of course I'm out on my differention. This text book is written in the most obscure way possible. I missed the lecture where we went over this. My head really hurts. I'm malnurished because college dining halls care more about being cheap than healthy. And I'm supposed to be a physics major...
20. ### Chain rule

Well I got this: cos(sin^2 x) * 2cosx *-sinx*cos(sin^2 x) + -sin(sin^2 x) * 2cosx * cosx *sin(cos^2 x) the back of the book gives me -sin2x cos(cos2x)
21. ### Chain rule

I don't understand it. How it works, etc... I've read the book definition, looked it up on the internet, and I still don't get it. Like the current problem I'm working on: derivative of sin((cos x)^2)*cos((sin x)^2)