Register Now

Login

Lost Password

Lost your password? Please enter your email address. You will receive a link and will create a new password via email.

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

Toán Lớp 8: Tìm x biết rằng a, (x^2+2x+4)*(2-x)+x*(x-3)*(x+4)-x^2+24=0 b, (x/2+3)*(5-6x)+(12x-2)*(x/4+3)=0

Tháng Mười Một 26, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Tìm x biết rằng
a, (x^2+2x+4)*(2-x)+x*(x-3)*(x+4)-x^2+24=0
b, (x/2+3)*(5-6x)+(12x-2)*(x/4+3)=0

Comments ( 2 )

  1. maianh67
    maianh67
    26 Tháng Mười Một, 2022 at 1:54 sáng
    Reply
    a)
    (x^2 + 2x + 4)(2-x) + x (x-3)(x+4) – x^2 + 24=0
    => -(x-2)(x^2 + 2x+4) + (x^2-3x)(x+4) – x^2 + 24= 0
    => – (x^3 – 2^3) + (x^3 + 4x^2 – 3x^2 – 12x) – x^2 + 24=0
    => -x^3 + 8 + x^3 + 4x^2 – 3x^2 – 12x – x^2 + 24 =0
    => (x^3 – x^3) + (4x^2 – 3x^2 – x^2) – 12x + (24+8)=0
    => -12x + 32 = 0
    => -12x = -32
    => x = 8/3
    Vậy x=8/3
    b)
    (x/2 + 3)(5-6x) + (12x – 2)(x/4 + 3) =0
    =>  ( 5/2x  – 3x^2 + 15 -18x) + ( 3x^2 + 36x – 1/2x -6)=0
    => 5/2 x – 3x^2 + 15 – 18x + 3x^2 + 36x – 1/2x -6=0
    => (-3x^2 + 3x^2) + (5/2x -18x + 36x – 1/2x) + (15-6)=0
    =>  20x + 9 =0
    => 20x = -9
    => x = -9/20
    Vậy x=-9/20
     

  2. bichquyenlien
    bichquyenlien
    26 Tháng Mười Một, 2022 at 1:53 sáng
    Reply
    Tìm x biết rằng:
    a, (x^2+2x+4)(2-x)+x(x-3)(x+4)-x^2+24=0
    =>(x^2 + 2x + 4).[-(x-2)] +(x^2 – 3x)(x+4) – x^2 + 24 = 0
    => – (x-2)(x^2 + 2x + 4)+(x^3 + 4x^2 – 3x^2 – 12x) – x^2 + 24 = 0
    => – (x^3 + 2x^2 + 4x – 2x^2 – 4x – 8)+(x^3 + 4x^2 – 3x^2 – 12x) – x^2 + 24 = 0
    => – (x^3 – 8) + (x^3 + 4x^2 – 3x^2 – 12x) – x^2 + 24 = 0
    => -x^3 + 8 + x^3 + 4x^2 – 3x^2 – 12x – x^2 + 24 = 0
    => -12x + 32 = 0
    => -12x = -32
    => x = (-32)/(-12)
    => x = 8/3
    Vậy x = 8/3
    b) (x/2+3)(5-6x)+(12x-2)(x/4+3)=0
    => (5/2 x – 3x^2 + 15 – 27x) + (3x^2 + 36x – 1/2 x – 6) = 0
    => 5/2 x – 3x^2 + 15 – 27x + 3x^2 + 36x – 1/2 x – 6 = 0
    => 20x+9 = 0
    => 20x = -9
    => x = (-9)/20
    => x = – 9/20
    Vậy x = – 9/20

Leave a reply

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

Thúy Hường

About Thúy Hường