Functional Vs Non Functional Requirement’s

Both will there in place then system will work as expected. 

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If Functional requirement will there but non-functional are not there then. Again it will cause for end user.
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 If non-functional requirement will there but functional are not there then. Again it will cause for end user.
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For more details about functional and non-functional requirement Clcik Functional_requirement & Non-functional_requirement