In: Advanced Math
Find two linearly independent solution of
y"+7xy=0. of the form
y1=1+a3x^3+a6x^6+....
y2=x+b4x^4+b7x^7+....
Enter the first few co-efficients
a3=
a6=
b4=
b7=
Let
y1=1+a3x^3+a6x^6+...
y'1=3a3x^2+6a6x^5+...
y"1=6a3x+30a6x^4+...
So
7xy=7x+7a3x^4+7a6x^7+...
Then
y"+7xy=0
Hence
(6a3x+30a6x^4)+(7x+7a3x^4+7a6x^7)=0
(6a3x+7x)+(30a6x^4+7a3x^4)=0
6a3+7=0 and 30a6+7a3=0
If you evaluate we find that,
a3=-7/6 then a6=49/180
To find b4 and b7,let
y2=x+b4x^4+b7x^7+...
y'2=1+4bx^3+7b7x^6+...
y"2=12b4x^2+42b7x^5+...
So
7xy=7x^2+7b4x^5+7b7x^8+...
y"+7xy=0
Then
(12b4x^2+42b7x^5)+(7x^2+7b4x^5+7b7x^8)=0
12b4x^2+7x2=0 and
42b7x^5+7b4x^5=0
We evaluate to get
b4=-7/12
b7=7/72
a3=-7/6
a6=49/180
b4=-7/12
b7=7/72