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

Toán Lớp 6: a)1/2-(-2/5)+1/3+5/7-(-1/6)+(-4/35)+1/41 b)1/100×99-1/99×98-1/98×97-…-1/2×1 mọi người ơi làm ơn

Toán Lớp 6: a)1/2-(-2/5)+1/3+5/7-(-1/6)+(-4/35)+1/41
b)1/100×99-1/99×98-1/98×97-…-1/2×1
mọi người ơi làm ơn

Comments ( 2 )

  1. a)
    1/2 – (-2/5) + 1/3 + 5/7 – (-1/6) + (-4/35) + 1/41
    = 1/2 + 2/5 + 1/3 + 5/7 + 1/6 – 4/35 + 1/41
    = (1/2 + 1/3 + 1/6) + (2/5 + 5/7 – 4/35) + 1/41
    = 1 + 1 + 1/41
    = 83/41
    b)
    1/(100×9) – 1/(99×98) – 1/(98×97) – ……. – 1/(2 × 1)
    = 1/(100×9) – (1/(99×98) + 1/(98×97) + ……. + 1/(2 × 1))
    = 1/9900 – (1/99 – 1/98 + 1/98 – 1/97 + ………… + 1/2 – 1)
    = 1/9900 – (1/99 – 1)
    = 1/9900 – (-98/99)
    = 1/9900 + 9800/9900
    = 9801/9900

  2. a, 1/2 – (-2/5) + 1/3 + 5/7 – (-1/6) + (-4/35) + 1/41
    = 1/2 + 2/5 + 1/3 + 5/7 + 1/6 – 4/35 + 1/41
    = ( 1/2 + 1/3 + 1/6 ) + ( 2/5 + 5/7 – 4/35 ) + 1/41
    = ( 3/6 + 2/6 + 1/6 ) + ( 14/35 + 25/35 – 4/35 ) + 1/41
    = 1 + 1 + 1/41
    = 2 + 1/41
    = 83/41
    b, 1/100.99 – 1/99.98 – 1/98.97 -………….- 1/2.1
    = 1/100.99 – ( 1/99.98 + 1/98.97 +………….+ 1/2.1 )
    = 1/100.99 – ( 1/99 – 1/98 + 1/98 – 1/97 +………+ 1/2 – 1 )
    = 1/100.99 – ( 1/99 – 1 )
    = 1/100.99 – (-98/99)
    = 1/9900 + 98/99
    = 99/100
     

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

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