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If you're using a tablet running Android 4.5 (Lollipop) or later and have forgotten your lock pattern, you'll need to reset your tablet back to its original factory settings. If you aren't able to use Find My Device to reset the tablet, you can use the keys on the tablet.  All data on the tablet will be lost unless you've already backed it up. If you've enabled Smart Lock to automatically unlock your Android in certain physical locations (such as your home or office), you can just bring the tablet to that location to get back in. You can lift your fingers once the tablet powers on. The buttons used to enter the recovery menu vary by model. If this combination doesn't work, try Volume Down and Power. Check your manufacturer's website to find the exact combination for your model. Here's how to do this on popular models:   Samsung: When the tablet boots to the Samsung screen, use the Volume Up button to select the icon of an Android with an arrow, press the Volume Down button, press Volume Down again to highlight Recovery Console, and then press the Power button.   LG: When you see the "Start" menu, press Volume Down twice to highlight Recovery Mode, and then press the Power button to select it.   Google Pixel:  Press the Volume Down button to highlight Restart bootloader, then press Power to select it. Use the volume keys to navigate to this menu option, then press Power to select it. This option may say Yes, delete all user data on some tablets, and you can use the Power button to select it. The tablet will then reset to its original factory settings. Once the reset is complete, you'll be prompted to restart the tablet. This option may not be required on all tablets. Once your tablet is reset, you'll be prompted to set it up as new. Log in with your Google account, and then follow the on-screen instructions to get your tablet back online. The setup process will also walk you through the process of protecting your Android with a new pattern, PIN, password, or biometric to unlock it in the future.

Summary:
Turn off your tablet. Press and hold the Volume Up and Power buttons simultaneously. Go to the recovery console. Scroll to and select Wipe Data / Factory Reset. Select Yes to confirm. Select Reboot System Now to complete the process. Set up your tablet as new.