Consider the IVP y"-y'=0 where y(0)=2 and y'(0)=3.Solve it using Laplace transforms

BenoguigoliB

BenoguigoliB

Answered question

2021-09-11

Consider the IVP yy=0 where y(0)=2andy(0)=3.Solve it using Laplace transforms

Answer & Explanation

coffentw

coffentw

Skilled2021-09-12Added 103 answers

Step 1
y"y=0   (1)
where y(0)=2andy(0)=3
Step 2
Using Laplace transform
L{y(t)}=sL{y(t)}y(0)
And
L{y"(t)}=s2L{y(t)}sy(0)y(0)
Step 3
Applying the Laplace transform on both sides in (1)
L{y"(t)}L{y(t)}=L{0}
s2L{y(t)}sy(0)y(0)sL{y(t)}+y(0)=0
s2L{y(t)}2s3sL{y(t)}+2=0
s2L{y(t)}2ssL{y(t)}1=0
L{y(t)}(s2s)=1+2s
L{y(t)}=1+2ss(s1)   (2)
Step 4
The partial fraction decomposition of
1+2ss(s1)=As+Bs1
1+2s=A(s1)+Bs
1+2s=AsA+Bs
Equating the coefficient of s and constant term
A+B=2
and A=1
1+B=2
B=3
1+2ss(s1)=1s+3s1
Step 5
From (2)
L{y(t)}=1s+3s1
y(t)=L1{1s+3s1}
y(t)=L1{1s}+L1{3s1}
y(t)=L1{1s}+3L1{1s1}
y(t)=t+3et

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