var btnGo= findViewById<Button>(R.id.btnGo)

            btnGo.setOnClickListener{
                val intent = Intent(this, manhinh2::class.java)
                startActivity(intent)
            }




var btnQuayLai = findViewById<Button>(R.id.btnQuayLai)
        btnQuayLai.setOnClickListener {
            val i = Intent (this, MainActivity::class.java)
            startActivity(i)
            }
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