You could never hold your finger on an app to close it...that would cause the icon to 'jiggle' and then delete from your phone permanently after pressing the 'X'.
To close an app from running the background, double-tap the home button and then swipe UP on the open app preview window that is above the app icon.
Thank you for your answer
I did mean after double-tapping the home button, then holding the icon of the app you want to close until the red minus sign appears then touching it to close it. Previous to ios 7, this is how my iPhone closed open apps, now it has changed to the "swiping up" on the app, but I didn't know that till I posted this question and then saw someone else who also had asked this question and received this information, lol.
Thank you for taking the time to write.....