Question

Tính tổng các số nguyên thỏa mãn

a/ -8<x<0

b/ -100<x<99

c/ -5 < x < hoặc bằng 4 

d/-2 < hoặc bằng x < 5

e/ -10 <x < 5 

f/ -10 < hoặc bằng x < hoặc bằng 10

Answer 1

`a)-8 < x < 0`        Mà `x in ZZ`

  `=>x in {-7;-6;-5;-4;-3;-2;-1}`

`=>T=-7-6-5-4-3-2-1=-28`

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`b)-100 < x < 99`     Mà `x in ZZ`

 `=>x in {-99;-98;-97;...;97;98}`

 `=>T=-99+(-98)+(-97)+...+97+98=[(-98)+98]+[(-97)+97]+...+(-99)=-99`

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`c)-5 < x <= 4`  Mà `x in ZZ`

  `=>x in {-4;-3;-2;-1;0;1;2;3;4}`

 `=>T=-4+4-3+3-2+2-1+1+0=0`

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`d)-2 <= x < 5`    Mà `x in ZZ`

   `=>x in {-2;-1;0;1;2;3;4}`

 `=>T=-2+2-1+1+0+3+4=7`

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`e)-10 < x < 5`    Mà `x in ZZ`

   `=>x in {-9;-8;-7;-6;-5;-4;-3;-2;-1;0;1;2;3;4}`

 `=>T=-4+4-3+3-2+2-1+1+0-9-8-7-6-5=-35`

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`f)-10 <= x <= 10`

   `=>x in {-10;-9;-8;...;8;9;10}`

  `=>T=-10+10-9+9-...-5+5=0`