Question

y''+4y'+4y=0

Answer 1

i apologies

Answer 2

No worries, I'm just telling you why I closed it.
Please don't use this space for self-advertisement. Please restrict social interactions to chat.
Thanks.

Answer 3

i'm really sorry.... it won't happen again,

how wud u solve this differential eqn:

y''+4y'+4y=0

Answer 4

I would find the roots of the characteristic polynomial.

Answer 5

x=-2 twice?

Answer 6

yes

Answer 7

so do you know how that affects the general solution?

Answer 8

affect?

u mean if my solution has doubled?

Answer 9

yeah, the double root I mean

Answer 10

my answer wud be

y=Ae^2t+Bxe^2t

Answer 11

i just add an "x" to C2

Answer 12

well, a 't' if you want to use t in the exponents :P

Answer 13

lol... that's what i crammed (O__o) thanks

Answer 14

and as you pointed out, the roots are negative, so so should be the exponents.

Answer 15

y=Ae^(-2t)+Bxe^(-2t)
so given initial conditions y(0)=0 and y(1)=0

i have to find y(3)

Answer 16

you should really be careful not to use x when you mean t, it will confuse you.
y=Ae^2t+Bte^2t
so by plugging in the initial values what do you get?

Answer 17

geez... forgot ut "t"

Answer 18

ahhhh.. that's where i get confused... what happens to the "t" after substitution

Answer 19

0=A+Bt?? for y(0)

Answer 20

oops, I mean negative
y=Ae^(-2t)+Bte^(-2t)
0=Ae^(-2(0))+B(0)e^(0)

Answer 21

you have an extra t... what is the value of t we are evaluating?

Answer 22

when t=0.5

Answer 23

well that is different...

Answer 24

is it given al da time?

Answer 25

tell me the initial conditions again

Answer 26

wait... the substitutions am makin on "t"???

Answer 27

t and y both

Answer 28

y(0)=0 means
y=0 when t=0

Answer 29

ow now i get it

so given initial conditions y(0)=0 and y(1)=0

i have to find y(3)

Answer 30

once you find y(t) it will be easy

Answer 31

0=A+B???

Answer 32

no, what is t?

Answer 33

ow... it becomes 0=A+B(0)


Then 0=Ae^(-2)+B(1)e^(-2).... y(1)

Answer 34

A=0

Answer 35

yes

Answer 36

so what do we have left?

Answer 37

I'M confused... so B=0 too?

Answer 38

yes

Answer 39

So the solution is y(t)=0, unless you typed it incorrectly

Answer 40

can we pls try one last non-homo question?

Answer 41

please post it separately as a new question
thanks