Recent content by bonildo

got it , thanks

Ok, got to a((1-t)x1+tx2)+b((1-t)y1+ty2)<=c . But why it proof that X is convex ?

This exercise is located in the vector space chapter of my book that's why I am posting it here. Recently started with this kind of exercise, proof like exercises and I am a little bit lost Proof that given a, b, c real numbers, the set X = {(x, y) E R^2; ax + by <= c} ´is convex at R^2 the...

I don't mean T=A , I mean T((1,1))=A*(1,1). In other words, the transformation applied to the vector (1,1) is equal to matrix A times (1,1). But I'm not sure if this equation is right... Did you get it ?

Summary:: linear transformations Hello everyone, firstly sorry about my English, I'm from Brazil. Secondly I want to ask you some help in solving a question about linear transformations. Here is the question:Consider the linear transformation described by the matrix \mathsf{A} \in \Re...

Homework Statement trying to solve |2x-1|-|x+5|-3=0: Homework Equations 3. The Attempt at a Solution [/B] for x>1/2 I got x=9 for -5<x<1/2 I got x=-7/3 but for x<-5 I got -(2x-1)-(-(x+5))-3=0 => x=3 (which is incorrect) why x=3 is incorrect , or why I shouldn't considerate the case x<-5 ?

Homework Statement Need to show that if A is not invertible then exist B (nxn) such that AB=0 but B is different from 0. Homework Equations The Attempt at a Solution Thought about writing A like E1...Ek*R where Ei are elementary matrices and R(different from I) the row reduced echelon matrice...

Yes, I do. But I can't still figure out a solution for it. I tried to solve s(0)= (1+ka*m(0)), but I don't know who is m(t)

Homework Statement Hello, the plot in the image shows a modulated signal s(t), with one period of the modulating signal m(t). The mean value of m(t) is equal to zero . Its asked me to find the modulated index, the amplitude of the carrier, the equation of the message(m(t)) and the kind of...

Homework Statement Hello, I'm not sure if it's the right place to post this exercise, but I'm learning it in a calculus course. I need to prove that: a) The complement of an open set is a closed. b) An open interval is a open set, a closed interval is a closed set. Homework Equations I have...

Homework Statement http://postimg.org/image/hf6zpmykr/ Homework Equations intrinsic carrier density = ni = 10^10/cm^3 (for Si at 300K) The Attempt at a Solution Its a really elementary problem but I can't figure out the difference between some quantities. For example, free electrons and holes...

Following vela's advice look what I got: http://www.wolframalpha.com/input/?i=integrate+%28sum_%28k%3D0%29%5Einfinity+%28-x%5E2%29%5Ek%2F%28k%21%29%29+from+0+to+x+#_=_

1. Write ∫e^(-t^2)dt with 0<=t<=x , as power series around 0. For what values of x this series converge ? attempt at a solution: f' = e^(-x^2) => f'(0) = 1 f''= -2x*e^(-x^2) => f''(0)= 0 f'''= -2e^(−x2) +4*x^2*e^(−x^2) => f'''(0)=-2 I tried to find a general rule for the derivatives but with...

Whais is the effect of a multiplication by (-1)^n in the DTFT ?? In other words, what's is this transform : x(n)* (-1)^n ??