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

Toán Lớp 8: bài 1: tìm x : a, 4(x+3)(3x-2)-3(x-1)(4x-1)=-27 b, 5x(12x+7)-3x(20x-5)=-100 c,(x+1)(x+2)(x+5)-x mũ 2 (x+8)=27

Tháng Chín 14, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: bài 1: tìm x :
a, 4(x+3)(3x-2)-3(x-1)(4x-1)=-27
b, 5x(12x+7)-3x(20x-5)=-100
c,(x+1)(x+2)(x+5)-x mũ 2 (x+8)=27

Comments ( 2 )

  1. myngocla
    myngocla
    14 Tháng Chín, 2022 at 11:07 chiều
    Reply
    Giải đáp + Lời giải và giải thích chi tiết:
    $#hyn$
    a) $4(x+3)(3x-2)-3(x-1)(4x-1)=-27$ 
    $⇒(4x+12)(3x-2)-(3x-3)(4x-1)=-27$
    $⇒(12x^2-8x+36x-24)-(12x^2-3x-12x+3)=-27$
    $⇒12x^2+28x-24-12x^2+15x-3=-27$
    $⇒43x-27=-27$
    $⇒43x=0$ $⇒x=0$ 
    b) $5x(12x+7)-3x(20x-5)=-100$ 
    $⇒5x.12x+5×7-3x.20x+3×5=-100$
    $⇒60x^2+35x-60x^2+15x=-100$
    $⇒35x+15x=-100$
    $⇒50x=-100$
    $⇒x=-2$
    c) $(x+1)(x+2)(x+5)-x^2(x+8)=27$ 
    $⇒(x^2+3x+2)(x+5)-x^3-8x^2=27$
    $⇒x^3+5x^2+3x^2+15x+2x+10-x^3-8x^2=27$
    $⇒17x+10=27$
    $⇒x=1$
     

  2. thaolanphuobg
    thaolanphuobg
    14 Tháng Chín, 2022 at 11:07 chiều
    Reply
    Giải đáp:
    Lời giải và giải thích chi tiết:
    a) 4(????+3)(3????−2)−3(????−1)(4????−1)=−27
    =>4????(3????−2)+12(3????−2)−3(????−1)(4????−1)=−27
    =>12????^2−8????+12(3????−2)−3(????−1)(4????−1)=−27
    =>12????^2−8????+36????−24−3(????−1)(4????−1)=−27
    =>12????^2+28????−24−3(????−1)(4????−1)=−27
    =>12????^2+28????−24−3????(4????−1)+3(4????−1)=−27
    =>12????^2+28????−24−12????2+3????+3(4????−1)=−27
    =>12????^2+28????−24−12????2+3????+12????−3=−27
    =>12????^2+28????−24−12????2+15????−3=−27
    =>12????^2+28????−27−12????2+15????=−27
    =>28????−27+15????=−27
    =>43????−27=−27
    =>43????=0
    =>????=0
    b)5????(12????+7)−3????(20????−5)=−100
    =>60????2+35????−3????(20????−5)=−100
    =>60????2+35????−60????2+15????=−100
    =>35????+15????=−100
    =>50????=−100
    =>x=−100/50
    =>????=−2
    c)0,6x(x – 0,5) – 0,3x(2x – 1,3) = 0,138
    <=>0,6x^2-0,3-0,6x^2+0,39x=0,138
    <=>-0,3+0,39x=0,138
    <=>0,39x=0,438
    <=>x=73/65≈1,12
    Lời giải và giải thích chi tiết:
     

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

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