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

Toán Lớp 8: Tìm x biết a) (5x – 1 ) ( 2x + 3 ) – 3 ( 3x – 1 ) =0 b) (x + 8 ) ( x + 6) – x ² = 104 c) ( 3x + 4 ) ( 5x – 1) + (5x + 2 ) ( 1 – 3x )

Home/ Toán Lớp 8: Tìm x biết a) (5x – 1 ) ( 2x + 3 ) – 3 ( 3x – 1 ) =0 b) (x + 8 ) ( x + 6) – x ² = 104 c) ( 3x + 4 ) ( 5x – 1) + (5x + 2 ) ( 1 – 3x )

Toán Lớp 8: Tìm x biết a) (5x – 1 ) ( 2x + 3 ) – 3 ( 3x – 1 ) =0 b) (x + 8 ) ( x + 6) – x ² = 104 c) ( 3x + 4 ) ( 5x – 1) + (5x + 2 ) ( 1 – 3x )

Tháng Mười Hai 4, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: Tìm x biết
a) (5x – 1 ) ( 2x + 3 ) – 3 ( 3x – 1 ) =0
b) (x + 8 ) ( x + 6) – x ² = 104
c) ( 3x + 4 ) ( 5x – 1) + (5x + 2 ) ( 1 – 3x ) = -2
d) 3( 2x – 1 ) ( x + 2 ) – 2 ( 3x + 2 ) ( x – 4) = 5

Comments ( 2 )

  1. quynhthanhnghi
    quynhthanhnghi
    4 Tháng Mười Hai, 2022 at 4:44 sáng
    Reply

    Đáp án câu a,b nè bạn
    toan-lop-8-tim-biet-a-5-1-2-3-3-3-1-0-b-8-6-104-c-3-4-5-1-5-2-1-3

  2. hoaiphuong85
    hoaiphuong85
    4 Tháng Mười Hai, 2022 at 4:44 sáng
    Reply
    $\rm a)\\(5x-1)(2x+3)-3(3x-1)=0\\⇔ 10x^2+15x-2x-3-9x+3=0\\⇔ 10x^2+(15x-2x-9x)-3+3=0\\⇔ 10x^2+4x=0\\⇔ 2x(5x+2)=0\\⇔ \left[ \begin{array}{l}2x=0\\5x+2=0\end{array} \right. ⇔ \left[ \begin{array}{l}x=0\\x=-\dfrac{2}{5}\end{array} \right.\\Vậy \ x \in \{ 0 ; -\dfrac{2}{5}\}\\b)\\(x+8)(x+6)-x^2=104\\⇔ x^2+6x+8x+48-x^2=104\\⇔ 14x=56\\⇔ x=4\\Vậy \ x = 4\\c)\\(3x+4)(5x-1)+(5x+2)(1-3x)=-2\\⇔ 15x^2-3x+20x-4+5x-15x^2+2-6x=-2\\⇔ 16x=0\\⇔ x=0\\Vậy \ x = 0 \\d)\\3(2x-1)(x+2)-2(3x+2)(x-4)=5\\⇔ 3(2x^2+4x-x-2)-2(3x^2-12x+2x-8)=5\\⇔ 3(2x^2+3x-2)-2(3x^2-10x-8)=5\\⇔ 6x^2+9x-6-6x^2+20x+16=5\\⇔ 29x=-5\\⇔ x=-\dfrac{5}{29}\\Vậy \ x = -\dfrac{5}{29}$

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

An Kim

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