Answer:
Therefore
and
are fundamental solution of the given differential equation.
Therefore
and
are linearly independent, since 
The general solution of the differential equation is

Step-by-step explanation:
Given differential equation is
y''-y'-20y =0
Here P(x)= -1, Q(x)= -20 and R(x)=0
Let trial solution be 
Then,
and 






Therefore the complementary function is = 
Therefore
and
are fundamental solution of the given differential equation.
If
and
are the fundamental solution of differential equation, then

Then
and
are linearly independent.




Therefore
and
are linearly independent, since 
Let the the particular solution of the differential equation is

and

Here
,
,
,and 

=0
and

=0
The the P.I = 0
The general solution of the differential equation is
