what is unresolved reference in kotlin code example

Example 1: Unresolved reference: kotlinx

plugins {    id'com.android.application'    id'kotlin-android'    id'kotlin-android-extensions'}

Example 2: unresolved reference launch kotlin

fun main() { 
    GlobalScope.launch { // launch a new coroutine in background and continue
        delay(1000L)
        println("World!")
    }
    println("Hello,") // main thread continues here immediately
    runBlocking {     // but this expression blocks the main thread
        delay(2000L)  // ... while we delay for 2 seconds to keep JVM alive
    } 
}