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

Toán Lớp 6: Rút gần biểu thức A=1/(x+1).(x+2)+1/(x+2).(x+3)…+1/(x+99).(x+100)+1/x+100

Toán Lớp 6: Rút gần biểu thức
A=1/(x+1).(x+2)+1/(x+2).(x+3)…+1/(x+99).(x+100)+1/x+100

Comments ( 2 )

  1. Giải đáp:
     A = 1/( (x + 1).(x + 2) ) + 1/( (x + 2) . (x + 3) ) + ………… + 1/( (x + 99) . (x + 100) ) + 1/(x + 100)
       = 1/(x + 1) – 1/(x + 2) + 1/(x + 2) – 1/(x + 3) + …. + 1/(x + 99) – 1/(x + 100) + 1/(x + 100)
       = 1/(x + 1)
     

  2. Giải đáp:
    A=1/{(x+1).(x+2)}+1/{(x+2).(x+3)}+…+1/{(x+99).(x+100)}+1/{x+100}
    ={(x+2)-(x+1)}/{(x+1).(x+2)}+{(x+3)-(x+2)}/{(x+2).(x+3)}+…+{(x+100)-(x+99)}/{(x+99).(x+100)}+1/{x+100}
    =1/{(x+1)}-1/{(x+2)}+1/{(x+2)}-1/{(x+3)}+…+1/{(x+99)}-1/{(x+100)}+1/{(x+100)}
    =1/{(x+1)}+(-1/{(x+2)}+1/{(x+2)})+…+(-1/{(x+99)}+1/{(x+99)})+(-1/{(x+100)}+1/{(x+100)})
    =1/{(x+1)}

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