Modelling of difference of a constant number and a variable in cvx

hello. I want to model theGP following term in cvx , but it shows error.
that I1(t),p1(t)) are variables. and error is
Error using .
(line 173)
Disciplined convex programming error:
Cannot perform the operation: {concave} .* {log-affine}

Error in project (line 91)
please help me.

I suggest you carefully read the chapter on Geometric Programming in the CVX User Guide . If you have read it, you have not understood it.

You’ll notice that the chapter includes a link to the tutorial on Geometric Programming at . I suggest you study that. The tutorial is not as terse as the CVX chapter.

thanks for your answer.