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- I don´t know whether I´m going to school tomorrow.
- He asked me whether I knew the way to San Diego
''Both if and whether are used in reporting questions which expect ‘yes’ or ‘no’ as the answer: She asked if/whether I wanted a drink., although whether sounds more natural with particular verbs such as discuss, consider and decide. When a choice is offered between alternatives if or whether can be used: We didn’t know if/whether we should write or phone. In this last type of sentence, whether is usually considered more formal and more suitable for written English.''
Use only whether after prepositions:
We talked about whether we should go or not.
I looked into whether he should stay.
Use only whether before infinitives:
She can't decide whether to buy the house or wait.
He considered whether to give up the position or quit next year.