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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: Tính: 1/98 – 1 / 98.97 – 1 / 87.86- … – 1/ 2.1

Tháng Mười 2, 2022 Toán học 2 Comments 0 views

Toán Lớp 7: Tính:
1/98 – 1 / 98.97 – 1 / 87.86- … – 1/ 2.1

Comments ( 2 )

  1. thanhtung
    thanhtung
    2 Tháng Mười, 2022 at 5:23 chiều
    Reply
    = $\dfrac{1}{98}$- ( $\dfrac{1}{98.97}$ + … +$\dfrac{1}{3.2}$ + $\dfrac{1}{2.1}$ )
    = $\dfrac{1}{98}$ – ( $\dfrac{1}{1.2}$ + $\dfrac{1}{2.3}$ + …. + $\dfrac{1}{97.98}$ )
    = $\dfrac{1}{98}$ – ( 1- $\dfrac{1}{2}$ + $\dfrac{1}{2}$ – $\dfrac{1}{3}$+ … + $\dfrac{1}{97}$ – $\dfrac{1}{98}$ )
    = $\dfrac{1}{98}$ – ( 1 – $\dfrac{1}{98}$ )
    = $\dfrac{1}{98}$ – 1 + $\dfrac{1}{98}$ 
    = ( $\dfrac{1}{98}$ + $\dfrac{1}{98}$ ) – 1 
    = $\dfrac{1}{49}$ – 1 
    = $\dfrac{-48}{49}$

  2. tuyethutanhthu
    tuyethutanhthu
    2 Tháng Mười, 2022 at 5:23 chiều
    Reply
    1/98 – 1/{98.97} – …- 1/{3.2} – 1/{2.1}
    = 1/98 – (1/{98.97} + …+ 1/{3.2} + 1/{2.1})
    = 1/98 – (1/{1.2} + 1/{2.3} +…+ 1/{97.98})
    = 1/98 – (1 – 1/2 + 1/2 – 1/3 +…+ 1/97 – 1/98)
    = 1/98 – (1 – 1/98)
    = 1/98 – 1 + 1/98
    = (1/98 + 1/98) – 1
    = 1/49 – 1
    = -48/49
     

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222-9+11+12:2*14+14 = ? ( )

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