In a system of parallel capacitors both have the same (delta)V. is it true that in that system, with power supplied by a battery of 9V, that each has a (delta)V of 4.5V? Or do they each have a (delta)V of 9V?
So both capacitors are in parallel across the battery? Then each capacitor must have a voltage of 9 V across it. After all, each capacitor is connected to either end (+ and -) of the battery.