Consider the following system of two first-order ODEs for y1(t) and y2(t) , y′1y′2=y1+8y2=2y1+3y2. Where y(t)=y1 , this system of differential equation is equivalent to a second-order ODE for y(t) of the form y′′−4y′+cy=0. What is the value of c ? Enter your integer valued answer below.
时间: 2023-06-26 18:05:37 浏览: 148
We can start by solving for y2 in the first equation:
y′1y′2 = 2y1 + 3y2
y′2 = (2y1 + 3y2) / y′1
Substituting this expression for y′2 into the second equation:
y′1(2y1 + 3y2) / y′1 = y1 + 8y2
2y1 + 3y2 = y1 + 8y2
y1 = 5y2
Substituting this relationship back into the first equation:
y′1y′2 = 2y1 + 3y2
y′1y′2 = 2(5y2) + 3y2
y′1y′2 = 13y2
Now we can differentiate both sides with respect to t:
y′′1y′2 + y′1y′′2 = 13y′2
Substituting y′2 = (2y1 + 3y2) / y′1:
y′′1(2y1 + 3y2) / y′1 + y′1(3y′1(2y1 + 3y2) - (2y1 + 3y2)y′′1) / y′1^2 = 13(2y1 + 3y2) / y′1
Simplifying:
2y′′1 + 9y′1^2 / y′1 - 3y′′1 = (26y1 + 39y2) / y′1
y′′1 - (4y′1) + (13/5)y1 = 0
Comparing with the standard form of a second-order ODE:
y′′ + py′ + qy = 0
We can see that c = 13/5.
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