Can we solve 1st order q-differential equations using

Charity Davies

Charity Davies

Answered question

2022-03-16

Can we solve 1st order q-differential equations using the usual methods of 1st order differential equations? For example, can we use integration factor method to solve this q-differential equations?
_qy(x)=a(x)y(qx)+b(xqy(x)=a(x)y(qx)+b(x)

Answer & Explanation

hinonacfp

hinonacfp

Beginner2022-03-17Added 3 answers

Step 1
Here is how to get a functional equation since you asked. Starting with a direct reference from q-Derivative from Wolfram MathWorld:
(d dx )qf(x)=f(x)f(qx)xqx
Therefore:
_q y(x)=a(x)y(qx)+b(xqy(x)=a(x)y(qx)+b(x)
=y(qx)y(x)x(q1)
=a(x)y(qx)+b(x)
which works for q1 since:
limq1_q y(xqy(x)
=limq1y(qx)y(x)x(q1)
=limq0y(x+q)y(x)q
=y(x)
=  y(xy(x)
= dy (x) dx 
but this limit is not needed when the q-Derivative is taken. Therefore we have our functional equation, rewritten:
Dqy(x)=a(x)y(qx)+b(x)y(qx)-y(x)x(q-1)=a(x)y(qx)+b(x)
Here is another form which also gives a recursive solution:
_q y(x)=a(x)y(qx)+b(x)\iff y(qx)-y(xqy(x)=a(x)y(qx)+b(x)y(qx)y(x)
=a(x)y(qx)x(q1)+b(x)x(q1)y(x)
=y(qx)(a(x)x(1q)+1)b(x)x(q1)
Please correct me and give me feedback!

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