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

Toán Lớp 6: S1 = 1 + (-3) + 5 + (-7) + … + 17 ; S2 = -2 + 4 + (-6) + 8 + … + (-18) Tính S1 + S2

Toán Lớp 6: S1
= 1 + (-3) + 5 + (-7) + … + 17 ;
S2
= -2 + 4 + (-6) + 8 + … + (-18)
Tính S1 + S2

Comments ( 2 )

  1. S1= 1 + (-3) + 5 + (-7) + … + 17
    = (1+5+…+17) + [ – ( 3 + 7 + … + 15 ) ]
    = 45 + (-36)
    = 9
    <=> S1 = 9
    S2 = -2 + 4 + (-6) + 8 + … + (-18)
    =[ – ( 2+ 6+ … + 18)] + ( 4+8+… + 16)
    =50 + ( – 40)
    =10
    <=> S2 = 10
    Ta có : S1 = 9 ; S2 = 10 
    => S1 + S2 <=> 9 + 10 = 19
    Vậy S1 + S2 = 19
    @thew

  2. S_1 = 1 + (-3) + 5 + (-7) + … + 17
    = ( 1 + 5 + … + 17 ) + [ – ( 3 + 7 + …. + 15 ) ]
    = 45 + (-36)
    = 45 – 36
    = 9
    – Vậy S_1 = 9
    S_2 = (-2) + 4 + (-6) + 8 + … + (-18)
    = [ -(2 + 6 + … + 18 ) ] + ( 4 + 8 + … + 16 )
    = 50 + (-40)
    = 50 – 40
    = 10
    – Vậy S_2 = 10
                                                                                          
    – Tính S_1 + S_2
    = 9 + 10
    = 19
    – Vậy S_1 + S_2 = 19
    @Tina

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

About Thúy Mai