how to sum up a range of formulas?

[Melissa]

I have 3 columns and 3 rows:
A1 B1 C1
A2 B2 C2
A3 B3 C3

In row 4, i have the formula: (A1+A2)*A3 which is applied to columns B and C
Is there a formula which allows me to sum up row 4 without first obtaining
the values by columns A, B and C? i.e. something like:
sum((A1+A2)*A3,(B1+B2)*B3,(C1+C2)*C3)... but I don't want to type it out...
just drag and fill?

 

[T. Valko]

Not sure what you mean by:

but I don't want to type it out... just drag and fill?

sum((A1+A2)*A3,(B1+B2)*B3,(C1+C2)*C3)

This formula does the same thing as the one above:

=SUMPRODUCT(A1:C1+A2:C2,A3:C3)

 

[Melissa]

My apologies for the unintelligible message and my thanks for your
suggestion.
In reality, my formula is more complex than the one given. What I'm
actually looking for is this: E f(x) (where E is the "sum of" symbol)
So, I need to specify what f(x) is, and apply that across my columns.
Instead of =sum(no.1, no.2, no.3, etc.), I would like =sum(f(x1), f(x2),
f(x3), etc.)

I hope this makes more sense...

 

[T. Valko]

Sorry, not following you on this.

 

[Melissa]

I realised I was overcomplicating things and using sumproduct works
perfectly. I just need to be extra careful in defining the ranges in the
formula. Thank you very much for that tip and sorry again for the confusion.

 

[T. Valko]

You're welcome. Thanks for the feedback!