Recent content by fufufu

thanks for the help.. What form should the solution be in? i just need to know if i am combining the equations correctly.. here's what i did: x' = 3x - 4y...1 y' = 2x + 3y....2 solved for X(s) in 1 X(s) = -4Y(s)(1/s-3) + 1/s-3 took inverse L.T. of X(s) x(t) = -4Y(s)(e^3t) + e^3t inserted...

Homework Statement y'' + 4y' + 2y = u_pi(t) + u_2pi(t) y(0) = 0 and y'(0) = 0.Homework Equations the step function equation: u_c(t) = u(t-c) --> (laplace) --> e^-cs/sThe Attempt at a Solution i am having major probs with getting my head around step function probs wrt laplace transforms. What...

thanks for help... ok i don't know why i was having probs with Y(s)...anyway i get Y(s) = 1/s+1 y(t) = e^-t next solve other equation + inv L.T., then solve 2 equations 2 unknowns to get y(t) = and x(t) =? thanks again (also, is this the method to use for all these kinds of problems? (system...

Homework Statement x' = 3x - 4y y' = 2x + 3y x(0) = 1 y(0) = 0Homework Equations y' = sY(s) - y(0) The Attempt at a Solution i am confused as to how to take laplace of either equation when i am left with a term i can't take the laplace of: specifically, x' = 3x - 4y sX(s) - 1 -3X(s) = -4Y(s)...

Thanks for the reply. yup you're right i copied down one of the IV's wrong; should be y(0) = 1 and y'(0) = 0. But I actually solved with the correct IV's, so my Y(s) is the same: heres how i got it s^2Y(s) -sf(0) - f'(0) + 4Y(s) = 2/(s^+4) Y(s) = 2 / (s^2+4)^2 + s/(s^2+4) Y(s) = 2/(s^2+4)^2...

Homework Statement y'' + 4y = sin(2t) y(0) = 1 y'(0) = 1 Homework Equations cramers ruleThe Attempt at a Solution after isolating Y(s) i end up with: Y(s) = 2 / (s^2+4)^2 + s/(s^2+4) after i do partial fraction decomposition, i get 4 equations with 4 unknowns, A, B, C and D i inserted B...

thanks for the help..yup i see it: (As+B)(s-3) makes all the difference, giving me C=3, B=4 and A = -3...now matches book solution.. but have follow-up question.. If I start solving equation with what I think is a fully decomposed denominator, when denominator could actually be decomposed...

Homework Statement y' - 3y = 13cos(2t) y(0)=1Homework Equations y' = sY(s) - y(0)The Attempt at a Solution heres all my work.. i am confused as to why its not matching book solution.. i think (geussing) that I probably messing up the decomposition step..thanks for any help with this...

Homework Statement what is general solution of 2y'' - 3y' + y = ((t^2) + 1)e^tHomework Equations my particular solution is: (e^t) ((2/3)(t^3) + 6t -4)) prof particular solution is: ((1/3)(t^3)(e^t)) - 2(t^3)(e^t) + 9(te^t) The Attempt at a Solution here is how i solved , i hope this is ok to...

Is it OK to post link to pdf of a homework problem (google docs) instead of typing it all out? I am just asking because I am really slow typing math stuff and its faster/easier to post link to the prob.. will my homework questions just get ignored if i do this or is this acceptable ? thanks...

Homework Statement What is the general solution of tv' + v = 0? book says it is v(t) = c/t but i don't see how i tried to solve like this: v' + (1/t)v = 0 p(t) = 1/t P(t) = Ln(t) y = e^ln(t) + c = t + e^c please help,thanks Homework Equations The Attempt at a...

Homework Statement 4y'' - 4y' + y = 0 y(1) = -4 y'(1) = 0 Homework Equations getting the coeff's gets messier and messier.. am i doing something wrong? The Attempt at a Solution 4y'' - 4y' + y = 0 y'' - y' - (1/4)y = 0 r_1 = r_2 = 1/2 general soln: y(t) = c_1e^(t/2) +...

what is the sine of "i" (initial value prob) Homework Statement What is the sine or cosine of i? does it make sense to ask what sine of root (-1) is? im asking because its from 2nd order DE: t^2y'' - ty' + y = 0...y(1) = 1 y'(1) = 1 when i rearrranged and determined omega it ended...

2nd order DE..."largest interval" confusion Homework Statement Determine the largest t-interval on which therem 3.1 guarantees the existence of a unique solution: y'' + 3t^2y' + 2y = sin(t) ...y(1) = 1 ...y'(1) = -1 Homework Equations theroem 3.1 is the one that states if p(t)...

Homework Statement R(dQ/dt) + (1/C)Q = E_0 e^-t ...Q(0) = 0 and E_0 = a constant Homework Equations The Attempt at a Solution first i rearranged to give: Q' + (1/CR)Q = (E_0e^-t)/R next i multiplied all by integrating factor of: u(t) = e^integ:(1/CR) = e^(t/CR)...