Google Play services out of date. Requires 10084000 but found 9879470. Can't update

Solution 1:

Updated 28 Feb 2017: Rev 4 of the emulator images for API 25 has been released and is available for download. It contains Google Play Services 10.2.98, which supports Firebase 10.2.0.

An emulator system image that supports Firebase 10.0.1 has not yet been released for API 25. The Rev 19 system image for API 23 does support 10.0.1.

You have three options:

1. Wait for release of an API 25 emulator system image that supports 10.0.1
2. Create an emulator device using Rev 19 of the API 23 system image. In the Standalone SDK Manager, the emulator images are grouped by API and have names like, "Google APIs...System Image". Make sure you have Rev 19 installed.
3. In your build, downgrade to a previous version of Firebase to allow use of the API 25 emulator image.

When running the emulated device, you can see the version of Google Play Services installed by going to Settings > Apps and selecting Google Play Services.

Solution 2:

I just solved it by changing the version of the dependencies. just use:

compile 'com.google.firebase:firebase-core:9.6.0'
compile 'com.google.firebase:firebase-auth:9.6.0'