Determine the values of r or which the given differential

tapetivk

tapetivk

Answered question

2021-11-17

Determine the values of r or which the given differential equation has solutions of the form y=ert, y3y+2y=0

Answer & Explanation

Florence Evans

Florence Evans

Beginner2021-11-18Added 16 answers

Plug ert into the equation. Recall that
(dndt)nert=rrt
y3y+2y=0
r3ert3r2ert+2rert=0
We can cancel out ert, since ert>0 for all t, then factor the remaining polynomial.
ert(r33r2+2r)=0
r33r2+2r=0
r(r23r+2)=0
r(r1)(r2)=0
This implies that ert is a solution only if r=0, r=1, r=2
Result: r=0, r=1, r=2

user_27qwe

user_27qwe

Skilled2023-06-10Added 375 answers

Step 1:
The first derivative of y is:
y=ddt(ert)=rert.
Similarly, the second derivative of y is:
y=ddt(rert)=r2ert.
Now we can substitute these derivatives into the differential equation:
r2ert3rert+2rert=0.
We can factor out the common term ert to simplify the equation:
ert(r23r+2)=0.
For this equation to hold, either ert=0 or (r23r+2)=0. However, ert is always positive, so it cannot be equal to zero. Therefore, we focus on the quadratic equation r23r+2=0.
Step 2:
To solve the quadratic equation, we can factor it as:
(r1)(r2)=0.
This implies that either r1=0 or r2=0. Solving these equations gives us two possible values for r:
r1=1andr2=2.
Therefore, the differential equation y3y+2y=0 has solutions of the form y=ert for r=1 and r=2.
karton

karton

Expert2023-06-10Added 613 answers

Solution:
Given the differential equation:
y3y+2y=0
We can substitute y=ert and its derivatives into the equation:
d2dt2(ert)3ddt(ert)+2(ert)=0
Taking the derivatives:
r2ert3rert+2ert=0
Factoring out ert:
ert(r23r+2)=0
Since ert is never zero, we can solve the quadratic equation:
r23r+2=0
To find the values of r, we can factorize the quadratic equation:
(r1)(r2)=0
Setting each factor to zero:
r1=0orr2=0
Solving for r:
r=1orr=2
Therefore, the values of r for which the given differential equation has solutions of the form y=ert are r=1 and r=2.
The solutions to the differential equation can be expressed as:
y1=etandy2=e2t

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