Bài 1 tính nhanh A. -785+{-801-[184-(184+801+785)]} B.-126-{790+[-157-(126-790-157)]}

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1. A=−785+{−801−[184−(184+801+785)]}A=-785+{-801-[184-(184+801+785)]}

   ⇔A=−785−801−184+184+801+785⇔A=-785-801-184+184+801+785

   ⇔A=(184−184)+(801−801)+(785−785)⇔A=(184-184)+(801-801)+(785-785)

   ⇔A=0⇔A=0

   B=−126−{790+[−157−(126−790−157)]}B=-126-{790+[-157-(126-790-157)]}

   ⇔B=−126−790+157+126−790−157⇔B=-126-790+157+126-790-157

   ⇔B=−790−790⇔B=-790-790

   ⇔B=−1580

    

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2. `A= -785+{-801-[184-(184+801+785)]} `

   `⇔A= -785-801-184+184+801+785`

   `⇔A= (184-184)+(801-801)+(785-785)`

   `⇔A=0`

   `B=-126-{790+[-157-(126-790-157)]}`

   `⇔B=-126-790+157+126-790-157`

   `⇔B=-790-790`

   `⇔B=-1580`

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