Bài 1 bỏ ngoặc 31-(26-(2017+35)) 913-(913+35) (351-275)-(215-149) -(330-97)-(-139+17) (219-)

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1. Bài 1

   31-[26-(2017+35)]

   =31-26+2017+35

   =2057

   $\\$

   913-(913+35)

   =913-913-35

   =-35

   $\\$

   (351-275)-(215-149)

   =351-275-215+149

   =(351+149)-(275+215)

   =500-490

   =10

   $\\$

   -(330-97)-(-139+17)

   =-330+97+139-17

   =(-330+139)+(97-17)

   =-191+80

   =-111

   $\\$

   [219-(-420)]-(119-220)

   =219+420-119+220

   =(219-119)+(420+220)

   =100+640

   =740

   $\\$

   Bài 2

   Ta có B(14)=0;14;28;42;56;70;84;98;…

   Vì 30<x<75

   =>x in{42;56;70}

   Trả lời