- #1

- 457

- 0

## Homework Statement

For what values of K does the function y=cos k t satisft the differential equation 4y"=-25y?

Do I have to find the derivative of y twice or what do i do

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- Thread starter afcwestwarrior
- Start date

- #1

- 457

- 0

For what values of K does the function y=cos k t satisft the differential equation 4y"=-25y?

Do I have to find the derivative of y twice or what do i do

- #2

- 1,753

- 1

... what does y'' mean?

- #3

- 457

- 0

it means second order derivative I believe

- #4

- 737

- 0

Yes, find the second derivative and compare constants.

- #5

- 457

- 0

ok so it would be y"=-k^2cos kt

- #6

- 737

- 0

Yes.

- #7

- 457

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then do i plug in values for it

- #8

Gib Z

Homework Helper

- 3,346

- 6

You have 4y"=-25y. Substitute what you know to be y and y'', and equate coefficients as Tedjn said.

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