1.He asked me why I didn't run and fetch the doctor.

2.He asked me to run and fetch the doctor.

I wanted to know which sentence is more natural and formal for reprted speech.

  • Why not? I am puzzled as to why @Josh has deleted his answer. – WS2 Jan 30 '17 at 11:53
  • Why not include in your question the research you've done? :) – NVZ Jan 30 '17 at 11:57
  • 1
    I think Longman is referring to "Why not?" as an entire reply to a question. Your example just uses uses why and not in the same sentence. – jimm101 Jan 30 '17 at 12:53
  • I'm voting to close this question as off-topic because it is a misinterpretation of a reference book. – jimm101 Jan 30 '17 at 12:54
  • I have edited my question. – learner Jan 30 '17 at 14:14

In answer to OP's original [amended here]

According to Longman Dictionary [reference needed],

"Why not" is a "spoken phrase" used to say that you agree with a suggestion.

My question is: Can I use Why not? in 'formal writing' as in the following sentence:

We then thought we might investigate whether an increase in the temperature resulted in a better yield. Why not?

According to Wordreference.com:

why not interj informal

(expressing openness to try [sth])

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