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

Toán Lớp 8: Tìm x: a/(4x+1)(x-3)-(x-7)(4x-1)=15 b/(x-2)(5x-1)-5x(x-3)=5 c/-4x^2(x-7)+4x(x^2-5)=28x^2-13 d/(3x-5)(x+1)-(3x-1)(x+1)=x-4

Home/ Toán Lớp 8: Tìm x: a/(4x+1)(x-3)-(x-7)(4x-1)=15 b/(x-2)(5x-1)-5x(x-3)=5 c/-4x^2(x-7)+4x(x^2-5)=28x^2-13 d/(3x-5)(x+1)-(3x-1)(x+1)=x-4

Toán Lớp 8: Tìm x: a/(4x+1)(x-3)-(x-7)(4x-1)=15 b/(x-2)(5x-1)-5x(x-3)=5 c/-4x^2(x-7)+4x(x^2-5)=28x^2-13 d/(3x-5)(x+1)-(3x-1)(x+1)=x-4

Tháng Tám 23, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Tìm x:
a/(4x+1)(x-3)-(x-7)(4x-1)=15
b/(x-2)(5x-1)-5x(x-3)=5
c/-4x^2(x-7)+4x(x^2-5)=28x^2-13
d/(3x-5)(x+1)-(3x-1)(x+1)=x-4

Comments ( 2 )

  1. quynhthanhnghi
    quynhthanhnghi
    23 Tháng Tám, 2022 at 7:42 sáng
    Reply
    a) (4x + 1) (x – 3) – (x – 7) (4x – 1) = 15
    ⇒ 4x² – 12x + x – 3 – (4x² – x – 28x + 7) = 15
    ⇒ 4x² – 12x + x – 3 – 4x² + 29x – 7 = 15    
    ⇒ (4x² – 4x²) + (-12x + x + 29x) + (-3 – 7) = 15
    ⇒ 18x – 10 = 15
    ⇒ 18x = 15 + 10
    ⇒ 18x = 25
    ⇒ x = $\frac{25}{18}$ 
    b) (x – 2) (5x – 1) – 5x(x – 3) = 5
    ⇒ 5x² – x – 10x + 2 – 5x² + 15x = 5 
    ⇒ (5x² – 5x²) + (-x – 10x + 15x) + 2 = 5
    ⇒ 4x + 2 = 5
    ⇒ 4x = 5 – 2
    ⇒ 4x = 3
    ⇒ x = $\frac{3}{4}$ 
    c) -4x²(x – 7) + 4x(x² – 5) = 28x² – 13
    ⇒ -4x³ + 28x² + 4x³ – 20x = 28x² – 13
    ⇒ (-4x³ + 4x³) + 28x² – 20x = 28x² – 13
    ⇒ 28x² – 20x = 28x² – 13
    ⇒ 28x² – 20x – 28x² = -13
    ⇒ (28x² – 28x²) – 20x = -13
    ⇒ -20x = -13
    ⇒ x = $\frac{13}{20}$ 
    d) (3x – 5) (x + 1) – (3x – 1) (x + 1) = x – 4
    ⇒ 3x² + 3x – 5x – 5 – (3x² + 3x – x – 1) = x – 4
    ⇒ 3x² + 3x – 5x – 5 – 3x² – 2x + 1 = x – 4
    ⇒ (3x² – 3x²) + (3x – 5x – 2x) + (-5 + 1) = x – 4
    ⇒ -4x – 4 = x – 4
    ⇒ -4x – x = -4 + 4
    ⇒ -5x = 0
    ⇒ x = 0
    Chúc bn học tốt!!!!
    vote 5*, ctlhn nha

  2. maitrucloan
    maitrucloan
    23 Tháng Tám, 2022 at 7:42 sáng
    Reply
    a)
    $(=) 4x^2 – 12x+x-3-(4x^2 -x-28x+7)=15$
    $(=) 4x^2-12x+x-3-(4x^2-29x+7)=15$
    $(=) 4x^2-12x+x-3-4x^2+29x-7=15$
    $(=) 18x-10=15$
    $(=) 18x=15+10$
    $(=) 18x=25$
    $=) x=25/18$
    b)
    $(=) 5x^2 -x-10x+2-5x^2+15x=5$
    $(=) 4x+2=5$
    $(=) 4x=5-2$
    $(=) 4x=3$
    $=) x=3/4$
    c)
    $(=) -4x^3 + 28x^2 + 4x^3 -20x = 28x^2 -13$
    $(=) 28x^2 – 20x = 28x^2 -13$
    $(=) -20x=-13$
    $=) x=13/20$
    d)
    $(=) (x+1)[3x-5-(3x-1)] = x-4$
    $(=) (x+1)(3x-5-3x+1)=x-4$
    $(=) (x+1)(-4)=x-4$
    $(=)-4x-4=x-4$
    $(=)-4x=x$
    $(=) -4x-x=0$
    $(=) -5x=0$
    $=) x=0$

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

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