my apps are still not extending to my other monitor. I have a dual monitor and i can see the desktop extending but not any of the apps

That not the issue. When I'm working with large spreadsheets or large graphics, I need to span both monitors with the same application. When I have an app, like excel, open in the left monitor, I cannot grab the right edge of the app and extend it to the right monitor. The app is restricted to one monitor or the other. How do I set up my Macbook Pro Retina to span both monitors with a single application?

Hello pjayasekharan,

Thank you for using Apple Support Communities.

Based on your post, I see that your apps are not extending to your 2nd display. I use two monitors as well, so I know how important it is that it's set up the way you want. I'll be more than happy to assist you with this.

You will want to make sure a feature called Mirror Displays is enabled. Mirroring displays the same image on each display.

Use OS X: How to use multiple displays with your Mac in Mountain Lion and earlier, specifically, this section:

Video mirroring

Mirroring displays the same image on each display.

1. Make sure your additional display is properly connected and powered on.
2. From the Apple () menu, choose System Preferences.
3. From the View menu, choose Displays.
4. Click the Arrangement tab.
5. Enable (check) "Mirror Displays" in the bottom-left corner.

In the example below. the blue boxes represent each display that is connected. The white bar at the top of both boxes represents your menu bar and is shown on both displays when they are showing the same information.

Have a great day!