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step1：Open MacBook settings

 

step2：Click on Displays

step2-1：Expanded mode when unchecked    

step2-2：Copy mode when checked

step2-3：Expanded mode when unchecked

step2-4：Copy mode when checked

step2-5：Expanded mode when unchecked  

step2-6：Copy mode when checked

Step 3: Set the resolution

Step 3-1 Click the “Displays” option and select the display you want to change.

Step 3-2 Set the resolution to: 3840x2160

 Step 3-3 Select a refresh rate of 60Hz.