How to update a single value with laravel

Hello i want to update a single value on another table using laravel. This is the code i have done until now but doesnt seem to work:

        $amount = Product::findorFail($request->products[$i]);
        $total_value = $request->amount[$i] + $amount->amount;
        $amount->update(['amount', $total_value]);
        dd($total_value);

with dd i see that the result is correct but the update function is not, the query im trying to make is

update table set amount=x where id=y

>Solution :

You have multiple choices. The shortes are:

$amount->update(['amount'=> $amount->amount + request->amount[$i]]);

or

Product::findorFail($request->products[$i])->increment('amount', $request->amount[$i]);