Inserting same values to end of preexisting cell values

Hi, I was wondering whether there is a quick way to insert the exact same value to the end of a cell with preexisting values without altering the preexisting values?

For example, the preexisting formulas are as below:
=1+2
=1+3
=1+4

Say I wish to add "-1" to end of each cell so that the new formulas are as below:
=1+2-1
=1+3-1
=1+4-1

I've been manually copying and pasting the equivalent of "-1" into my preexisting array of cells - is there a faster way to do this? Thanks all.

Ideally I'd have the full formula. The reason is because I'm in a transaction process at the moment that sees the model being regularly updated, and with line items often being shifted. For purposes of efficiency, I'd ideally be able to link all the cells I need to change to one flex cell containing the relevant delta without having to insert additional lines.

Maybe, update your formulas to:

=1+2+A1
=1+3+A1
=1+4+A1

and then place the desired value in cell A1 (e.g., 0 or -1)

@Root_, yup that's what I've been doing at the moment. The issue is that given the formulas are inconsistent I'm not able to drag, and have to manually insert the "+A1" reference. Unfortunately there's a large number of lines that require this adjustment.

For a bit more context, I'm in the middle of project finance bid process where the financial model gets updated frequently, and sensitivity analysis has to be performed on it in relatively short turnaround times. The build of the model means that both the manual insertions method and inserting additional reference row methods are very time consuming. I was just wanting to see whether there was an easier option out there for when the next update of the model comes around.

It's more of a gliding action.

Thanks, however my understanding of the paste special function is that it hard-codes the results. For audit purposes, I need the full calculation to be traceable.