Question: Subtraction of two generalized hypergeometric functions

Greetings to all,

I am trying to evaluate anexpression of the form :   P * x₁F₂(a; 1+a-b; 1+a; x)  -  Q * x  * ₁F₂(b; 1+b-a; 1+b; x)   where P,Q,a and b are constants. I need to evalute this expression for large values of the parameter x ( in loop). Eventhough the value of the above expression is a small quantity nearing unity, individual values of the hypergeometric functions will be very huge, and hence can create problems with the resolution of the processing. One way is to change the resolution to some huge value on case by case basis. Is there any trick or method so that it may be possible to evaluate this expression using the smaller fixed resolution values?. Thank you very much for any help.

Best regards,

Vishwa