Question: How to print indexed names?

I have double indexed functiions f[j,k] of one variable and double indexed coefficients a[j,k].

I want my print do look like a[1,1]f11+a[1,2]f12 that is, the values of a[j,k] should appear beside the functions' names, like

7f11+2f12-3f21 etc.

Thank yopu for any help

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