• To force an app to close, right-click or control-click its icon in the Dock. If it's not responding, you'll be able to Force Quit it.
• It's time to reboot if you can't Force Quit an unresponsive application. Even if you were able to Force Quit your problematic app, it's still worth rebooting your machine.
• to Restart a Mac That Isn't Working: Hold the power button down for a few seconds. If it doesn't work, hold down the Control and Command buttons while pressing the Power button.
• The initial cause of your Mac's slowness is usually out-of-date software.
• Select System Preferences > Software Update from the Apple menu. You may check here to see if your Mac needs to be updated. To install an update, follow the on-screen instructions.

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