Differential Equation with an Initial condition

In summary: Good luck!In summary, the given differential equation is separable but can also be solved using the Bernoulli method. It can be rearranged into a first-order differential equation and solved using an integrating factor.
  • #1
Zinggy
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Homework Statement


x(dy/dx) = 3y +x4cos(x), y(2pi)=0

Homework Equations


N/A

The Attempt at a Solution


I've tried a couple different ways to make this separable, but you always carry over a 1/dx or 1/dy term and I can never fully separate this. I've also tried to do a Bernoulli differential equation method by doing a change of variable and putting it in the form: xy'-3y = x4cos(x) but it's not quite the right format to allow that to work, I would need it to be y4cos(x) instead.
 
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  • #2
Hint: Integrating factors.
 
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  • #3
Zinggy said:

Homework Statement


x(dy/dx) = 3y +x4cos(x), y(2pi)=0

Homework Equations


N/A

The Attempt at a Solution


I've tried a couple different ways to make this separable, but you always carry over a 1/dx or 1/dy term and I can never fully separate this. I've also tried to do a Bernoulli differential equation method by doing a change of variable and putting it in the form: xy'-3y = x4cos(x) but it's not quite the right format to allow that to work, I would need it to be y4cos(x) instead.
Divide both sides of the DE by ##x##. That gives a very standard first-order DE with a well-known solution. (Hint: the hint from #2).
 
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  • #4
Divide both sides by ##x## and rearrange into:
##\dot y -\frac 3 x y = x^3 cos(x)##
Since you are studying differential equations I trust that you can figure out how to solve this.
 
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