d2x/dt2 + 4dx/dt + 4x = 0 x(0) =2, x' (0)

Miguel Reynolds

Miguel Reynolds

Answered question

2021-12-16

d2xdt2+4dxdt+4x=0
x(0)=2,x(0)=1

Answer & Explanation

Beverly Smith

Beverly Smith

Beginner2021-12-17Added 42 answers

d2xd+2+4dxdt+4x=0
The equation
r2+4r+4=0
(r+2)2=0
r=2,2
The general equation
x=c1e2t+c2e2t
x(0)=c1e0
2=c1 eq(1)
x1=2c1e2t+x(2)c2e2t+c2e2t
x1(0)=2c1+0+c2
1=2c1+c2 eq(2)
Putting the value eqn (1) we get
1=2(2)+c2
1=4+c2
c2=5
Final equation x=2e2t+5tc2e2t
Mollie Nash

Mollie Nash

Beginner2021-12-18Added 33 answers

The given initial value problem is d2xdt2+4dxdt+4x=0,x(0)=2,x(0)=1.
The auxiliary equation is m2+4m+4=0
Obtain the roots of auxiliary equation as shown below.
m2+4m+4=0
m2+2m+2m+4=0
m(m+2)+2(m+2)=0
(m+2)(m+2)=0
m=2,2
Here, the roots are real and equal.
Therefore, the general solution of d2xdt2+4dxdt+4x=0 is x(t)=e2t(c1+c2t).
The derivative of x(t)=e2t(c1+c2t) is,
x(t)=e2t(0+c2(1))+e2t(2)(c1+c2t)
=e2tc22e2t(c1+c2t)
=e2t(c22c12c2t)
Now evaluate the constants using the initial conditions x(0)=2,x(0)=1 as shown below.
x(t)=e2t(c1+c2t)
x(0)=e2(0)(c1+c2(0))
2=(1)(c1)
c1=2
And,
RizerMix

RizerMix

Expert2021-12-29Added 656 answers

d2xd+2+4dxdt+4x=0r2+4r+4=0(r+2)2=0r=2,2x=c1e2t+c2e2tx(0)=c1e02=c1x1=2c1e2t+x(2)c2e2t+c2e2tx1(0)=2c1+0+c21=2c1+c21=2(2)+c21=4+c2c2=5
Answer: x=2e2t+5tc2e2t

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