android studio修改minSdkVersion

导入第三方的sdk'需要修改minSdkVersion，可是改了之后一直报以下错误：
Error:Execution failed for task ':app:processDebugManifest'.

Manifest merger failed : uses-sdk:minSdkVersion 8 cannot be smaller than version 9 declared in library [com.android.support:appcompat-v7:25.3.1] C:\Users\Weizhi.Shi.android\build-cache\e14beb946f83c1364b932d1d0a8187ffcbf64ba2\output\AndroidManifest.xml
Suggestion: use tools:overrideLibrary="android.support.v7.appcompat" to force usage

运行第三方的demo又运行不来，请大神帮忙！！！