How can I quickly close all my apps?

Apps running in the background taking too much memory, causing the system slow-down, operating seizure, app non-startups, app auto exit, app crashes, etc.

1. Hold or tap the "Multitasking button" to bring up recently used apps, then tap on the option "Close all"
2. Install a third-party app to quickly exit all apps running in the background with a single touch.