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

Toán Lớp 7: bài 1 tìm x: a, 3/4.x+1/5=1/6 b, 1/3+1/2:x=-4 bài 2 a, -20/35+16/24; B, -3/15–3/25; c -1/7 – 1/8 d 1/6-1/26

Toán Lớp 7: bài 1 tìm x: a, 3/4.x+1/5=1/6 b, 1/3+1/2:x=-4 bài 2 a, -20/35+16/24; B, -3/15–3/25; c -1/7 – 1/8 d 1/6-1/26

Comments ( 2 )

  1. Bài 1 :
    a) 3/4x + 1/5 = 1/6
    => 3/4x         = 1/6 – 1/5
    => 3/4x         = -1/30
    =>      x         = -1/30 : 3/4
    =>      x         = -2/45
    b) 1/3 + 1/2 : x = -4
    =>         1/2 : x = -4 -1/3
    =>         1/2 : x = -13/3
    =>                 x = 1/2 : -13/3
    =>                 x = -3/26
    Bài 2 :
    a) -20/35 + 16/24 = -480/840 + 560/840 = (-480 +560)/840 = 80/840 = 2/21 
    b) (-3)/15 – (-3)/25 = -1/5 – -3/25 = (-5)/25 – (-3)/25 = (-5 – (-3))/25 = -2/25
    c) -1/7 – 1/8 = -8/56 – 7/56 = (-8 – 7)/56 = -15/56
    d) 1/6 – 1/26 = 13/78 – 3/78 = (13 – 3)/78 = 10/78 = 5/39  
     

  2. Bài 1:
    a, 3/4.x+1/5=1/6
    ⇒ 3/4.x = 1/6 – 1/5
    ⇒ 3/4.x = -1/30
    ⇒ x = -1/30 : 3/4
    ⇒ x= -2/45
    b, 1/3+1/2:x=-4
    ⇒ 1/2 : x = -4 – 1/3
    ⇒ 1/2 : x = -13/3
    ⇒ x = -3/26
    Bài 2:
    a, -20/35+16/24
    = -4/7 + 2/3
    = -12/21 + 14/21
    = 2/21
    b, -3/15-(-3/25)
    = -1/5+3/25
    = -5/25+3/25
    = -2/25
    c, -1/7 – 1/8
    = -8/56 – 7/56
    = -15/56
    d, 1/6 – 1/26
    = 26/156 – 6/156
    = 20/156
    = 5/39

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