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

Toán Lớp 8: tìm x a) ( 5x –1)( x-4) -x( 5x –6) = 12 b) ( 3x –1)2–9x(x-3) = x+1 c) ( x –1)2–( x –2 ) ( x +2) = 0

Home/ Toán Lớp 8: tìm x a) ( 5x –1)( x-4) -x( 5x –6) = 12 b) ( 3x –1)2–9x(x-3) = x+1 c) ( x –1)2–( x –2 ) ( x +2) = 0

Toán Lớp 8: tìm x a) ( 5x –1)( x-4) -x( 5x –6) = 12 b) ( 3x –1)2–9x(x-3) = x+1 c) ( x –1)2–( x –2 ) ( x +2) = 0

Tháng Tám 15, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: tìm x
a) ( 5x –1)( x-4) -x( 5x –6) = 12 b) ( 3x –1)2–9x(x-3) = x+1
c) ( x –1)2–( x –2 ) ( x +2) = 0 d) 3x( x –7) –x ( 3x –5) = 16

Comments ( 2 )

  1. baoquyen
    baoquyen
    15 Tháng Tám, 2022 at 3:04 chiều
    Reply
    a) (5x – 1). (x – 4) – x. (5x – 6) = 12

    5×2 – 20x – x + 4 – 5×2 + 6x = 12

    (5×2– 5×2) + (-20x – x + 6x) + 4 = 12 

    -15x + 4= 12

    -15x= 8

    x=-8/15

    b) (3x – 1)2 – 9x. (x – 3) = x + 1

    (3x)2– 2.3x.1 + 12– 9×2+ 27x = x + 1

    9×2 – 6x + 1 – 9×2 + 27x = x + 1

    (9×2– 9×2) + (-6x + 27x) + 1 = x + 1

    21x+ 1 = x + 1

    21x – x = 1 – 1

    20x = 0

    x= 0

    c) ( x –1)2 – ( x –2 ) ( x +2) = 0      

    x2– 2.x.1 + 12– (x2– 22) = 0

    x2 – 2x + 1 – x2 + 4= 0

    (x2 – x2) – 2x + (1 + 4) = 0

    – 2x + 5= 0

    – 2x= -5

    x=5/2

    d) 3x( x – 7) – x. ( 3x – 5) = 16

    3×2 – 21x – 3×2. + 5x = 16

    (3×2– 3×2) + (-21x + 5x) = 16

    -16x = 16

    x = -1

  2. tuyen98
    tuyen98
    15 Tháng Tám, 2022 at 3:04 chiều
    Reply
          a) (5x – 1). (x – 4) – x. (5x – 6) = 12
        ⇒ 5x2 – 20x – x + 4 – 5x2 + 6x = 12
        ⇒(5x2 – 5x2) + (-20x – x + 6x) + 4 = 12 
        ⇒ -15x + 4       = 12
        ⇒ -15x               = 8
        ⇒   x               = $\frac{-8}{15}$ 
                   Vậy x = $\frac{-8}{15}$ 
          b) (3x – 1)2 – 9x. (x – 3) = x + 1
        ⇒ (3x)2 – 2.3x.1 + 12 – 9x2 + 27x = x + 1
        ⇒ 9x2 – 6x + 1 – 9x2 + 27x = x + 1
        ⇒ (9x2 – 9x2) + (-6x + 27x) + 1 = x + 1
        ⇒ 21x     + 1 = x + 1
        ⇒  21x – x = 1 – 1
        ⇒  20x = 0
        ⇒  x     = 0
                        Vậy x = 0
         c) ( x –1)2 – ( x –2 ) ( x +2) = 0       
        => x2 – 2.x.1 + 12 – (x2 – 22) = 0
        =>x2 – 2x + 1 – x2 + 4     = 0
        =>(x2 – x2) – 2x + (1 + 4) = 0
        =>            – 2x + 5            = 0
         =>           – 2x                   = -5
         =>                x                   = $\frac{5}{2}$ 
                     Vậy x = $\frac{5}{2}$ 
          d) 3x( x – 7) – x. ( 3x – 5) = 16
       => 3x2 – 21x – 3x2. + 5x = 16
       => (3x2 – 3x2) + (-21x + 5x) = 16
        =>-16x = 16
        => x = -1
                        Vậy x = -1
    Những cái dòng mà mk in đậm ý bạn cs thể viết vào cũng đc 
    Vì mk viết thế cho bạn hiểu
    Chúc bạn học tốt

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

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