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

Toán Lớp 8: Bµi 6. Tìm x, biết: a) (2x + 3)(x – 4) + (x – 5)(x – 2) = (3x – 5)(x – 4); b) (8x – 3)(3x + 2) – (4x + 7)(x + 4) = (2x + 1)(5x – 1);

Home/ Toán Lớp 8: Bµi 6. Tìm x, biết: a) (2x + 3)(x – 4) + (x – 5)(x – 2) = (3x – 5)(x – 4); b) (8x – 3)(3x + 2) – (4x + 7)(x + 4) = (2x + 1)(5x – 1);

Toán Lớp 8: Bµi 6. Tìm x, biết: a) (2x + 3)(x – 4) + (x – 5)(x – 2) = (3x – 5)(x – 4); b) (8x – 3)(3x + 2) – (4x + 7)(x + 4) = (2x + 1)(5x – 1);

Tháng Mười Một 11, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Bµi 6. Tìm x, biết:
a) (2x + 3)(x – 4) + (x – 5)(x – 2) = (3x – 5)(x – 4);
b) (8x – 3)(3x + 2) – (4x + 7)(x + 4) = (2x + 1)(5x – 1);
c) 2x² + 3(x – 1)(x + 1) = 5x(x + 1);
d) (8 – 5x)((x + 2) + 4(x – 2)(x + 1) + (x – 2)(x + 2);
e) 4(x – 1)( x + 5) – (x +2)(x + 5) = 3(x – 1)(x + 2)

Comments ( 2 )

  1. giahan44
    giahan44
    11 Tháng Mười Một, 2022 at 10:18 chiều
    Reply
    \(a)\)
    \(\left(2x+3\right)\left(x-4\right)+\left(x-5\right)\left(x-2\right)=\left(3x-5\right)\left(x-4\right)\)
    \(\Leftrightarrow2x^2-5x-12+x^2-7x+10=3x^2-17x+20\)
    \(\Leftrightarrow3x^2-12x-2-3x^2+17x-20=0\)
    \(\Leftrightarrow5x-22=0\)
    \(\Leftrightarrow x=\dfrac{22}{5}\)
    \(b)\)
    \(\left(8x-3\right)\left(3x+2\right)-\left(4x+7\right)\left(x+4\right)=\left(2x+1\right)\left(5x-1\right)\)
    \(\Leftrightarrow\left(8x-3\right)\left(3x+2\right)-\left(4x+7\right)\left(x+4\right)-\left(2x+1\right)\left(5x-1\right)=0\)
    \(\Leftrightarrow\left(24x^2+16x-9x-6\right)-\left(4x^2+16x+7x+28\right)-\left(10x^2-2x+5x-1\right)=0\)
    \(\Leftrightarrow24x^2+16x-9x-6-4x^2-16x-7x-28-10x^2+2x-5x+1=0\)
    \(\Leftrightarrow10x^2-19x-33=0\)
    \(\Leftrightarrow10x^2+11x-30x-33=0\)
    \(\Leftrightarrow\left(10x^2+11x\right)-\left(30x+33\right)=0\)
    \(\Leftrightarrow x\left(10x+11\right)-3\left(10x+11\right)=0\)
    \(\Leftrightarrow\left(10x+11\right)\left(x-3\right)=0\)
    \(\Leftrightarrow\left[{}\begin{matrix}10x+11=0\\x-3=0\end{matrix}\right.\)
    \(\Leftrightarrow\left[{}\begin{matrix}10x=-11\\x=3\end{matrix}\right.\)
    \(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-11}{10}\\x=3\end{matrix}\right.\)
    Vậy \(x=\dfrac{-11}{10}\) hoặc \(x=3\)
    \(c)\)
    \(2x^2+3(x-1)(x+1)=5x(x+1)\)
     \(\Leftrightarrow2x^2+3\left(x^2+x-x-1\right)=5x^2+5x\)
    \(\Leftrightarrow2x^2+3\left(x^2-1\right)=5x^2+5x\)
    \(\Leftrightarrow2x^2+3x^2-3=5x^2+5x\)
    \(\Leftrightarrow5x^2-3=5x^2+5x\)
    \(\Leftrightarrow5x=-3\)
    \(\Leftrightarrow x=\dfrac{-3}{5}\)
    Vậy \(x=\dfrac{-3}{5}\)
    \(d)\)
    \(\left(8-5x\right)\left(x+2\right)+4\left(x-2\right)\left(x+1\right)+2\left(x-2\right)\left(x+2\right)=0\)
    \(\Rightarrow8x+16-5x^2-10x+4\left(x^2+x-2x-2\right)+2\left(x^2-4\right)=0\)
    \(\Rightarrow16-5x^2-2x+4x^2-4x-8+2x^2-8=0\)
    \(\Rightarrow x^2-6x=0\Rightarrow x.\left(x-6\right)=0\)
    \(\Rightarrow\left[{}\begin{matrix}x=0\\x-6=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=6\end{matrix}\right.\)
    \(e)\)
    \(4(x – 1)( x + 5) – (x +2)(x + 5) = 3(x – 1)(x + 2)\)
    \(\Leftrightarrow(4x-4)(x+5)-(x^2+5x+2x+10)=(3x-3)(x+2)\)
    \(\Leftrightarrow4x^2+20x-4x-20-x^2-5x-2x-10=3x^2+6x-3x-6\)
    \(\Leftrightarrow3x^2+9x-3x^2-6x+3x=-6+10+20\)
    \(\Leftrightarrow6x=24\)
    \(\Leftrightarrow x=4\)

  2. thanhbinh2k5
    thanhbinh2k5
    11 Tháng Mười Một, 2022 at 10:17 chiều
    Reply
    Giải đáp + Lời giải và giải thích chi tiết:
    a) (2x + 3)(x – 4) + (x – 5)(x – 2) = (3x – 5)(x – 4)
    2x² – 8x + 3x – 12 + x² – 2x – 5x + 10 = 3x² – 12x – 5x + 20
    3x² – 12x – 2 – 3x² + 17x = 20
    5x = 22
    x = \frac{22}{5}
    b)
    (8x – 3)(3x + 2) – (4x + 7)(x + 4) = (2x + 1)(5x – 1)
    24x² + 16x – 9x – 6 – (4x² + 16x + 7x + 28) = 10x² – 2x + 5x – 1
    24x² + 7x – 6 – 4x² – 23x – 28 – 10x² – 3x + 1 = 0
    10x² – 19x – 33 = 0
    10x² + 11x – 30x – 33 = 0
    (x-3)(10x + 11) = 0
    \(\left[ \begin{array}{l}x=3\\x=-\dfrac{11}{10}\end{array} \right.\) 
    c)
    2x² + 3(x – 1)(x + 1) = 5x(x + 1)
    2x² + 3x² – 3 = 5x² + 5x
    5x² – 5x² – 3 = 5x
    5x = -3
    x = \frac{-3}{5}
    d)
    (8 – 5x)(x + 2) + 4(x – 2)(x + 1) + (x – 2)(x + 2) = 0
    8x + 16 – 5x² – 10x + 4(x² – x – 2) + x² – 4 = 0
    -5x² – 2x + 16 + 4x² – 4x – 8 + x² = 4
    -6x + 8 = 4
    6x = 4
    x = \frac{2}{3} 
    e) 4(x – 1)( x + 5) – (x +2)(x + 5) = 3(x – 1)(x + 2)
    4(x² + 5x – x – 5) – (x² + 7x + 10) = 3(x² + x – 2)
    4x² + 16x – 20 – x² – 7x – 10 – 3x² – 3x = -6
    6x – 30 = -6
    6x = 24
    x = 4

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

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