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

Toán Lớp 8: Tìm x, biết: a) 49² – 25 = 0 b)(4x – 1) ² – (3x + 2) ² = 0 c)(3x – 2) ³ – (3x – 2)(9x ² + 6x + 4) +27x(2x – 5) = 0

Home/ Toán Lớp 8: Tìm x, biết: a) 49² – 25 = 0 b)(4x – 1) ² – (3x + 2) ² = 0 c)(3x – 2) ³ – (3x – 2)(9x ² + 6x + 4) +27x(2x – 5) = 0

Toán Lớp 8: Tìm x, biết: a) 49² – 25 = 0 b)(4x – 1) ² – (3x + 2) ² = 0 c)(3x – 2) ³ – (3x – 2)(9x ² + 6x + 4) +27x(2x – 5) = 0

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

Toán Lớp 8: Tìm x, biết:
a) 49² – 25 = 0
b)(4x – 1) ² – (3x + 2) ² = 0
c)(3x – 2) ³ – (3x – 2)(9x ² + 6x + 4) +27x(2x – 5) = 0

Comments ( 2 )

  1. tuyen98
    tuyen98
    2 Tháng Mười Hai, 2022 at 11:37 sáng
    Reply
    a) 49x^2-25=0
    <=> (7x)^2-5^2=0
    <=> (7x-5)(7x+5)=0
    <=> [(7x-5=0),(7x+5=0):}
    <=>[(x=5/7),(x=-5/7):}
    Vậy S={+-5/7}
    b) (4x-1)^2-(3x+2)^2=0
    <=> (4x-1-3x-2)(4x-1+3x+2)=0
    <=> (x-3)(7x+1)=0
    <=> [(x-3=0),(7x+1=0):}
    <=>\(\left[ \begin{array}{l}x=3\\x=\dfrac{-1}{7}\end{array} \right.\) 
    Vậy S={3;-1/7}
    c) (3x-2)^3-(3x-2)(9x^2+6x+4)+27x(2x-5)=0
    <=> 27x^3-54x^2+36x-8-(27x^3-8)+54x^2-135x=0
    <=> 27x^3-99x-8-27x^3+8=0
    <=> -99x=0
    <=> x=0
    Vậy S={0}
     

  2. buithaianh98
    buithaianh98
    2 Tháng Mười Hai, 2022 at 11:37 sáng
    Reply
    Giải đáp + Lời giải và giải thích chi tiết:
    a)
    49x^{2}-25=0
    <=>(7x-5)(7x+5)=0
    <=> \(\left[ \begin{array}{l}7x-5=0\\7x+5=0\end{array} \right.\) 
    <=> \(\left[ \begin{array}{l}x=\dfrac{5}{7}\\x=-\dfrac{5}{7}\end{array} \right.\) 
    Vậy S={+-(5)/(7)}
    b)
    (4x-1)^{2}-(3x+2)^{2}=0
    <=>(4x-1+3x+2)(4x-1-3x-2)=0
    <=>(7x+1)(x-3)=0
    <=> \(\left[ \begin{array}{l}7x+1=0\\x-3=0\end{array} \right.\) 
    <=> \(\left[ \begin{array}{l}x=-\dfrac{1}{7}\\x=3\end{array} \right.\) 
    Vậy S={-(1)/(7);3}
    c)
    (3x-2)^{3}-(3x-2)(9x^{2}+6x+4)+27x(2x-5)=0
    <=>27x^{3}-54x^{2}+36x-8-(27x^{3}-8)+54x^{2}-135x=0
    <=>27x^{3}-54x^{2}+36x-8-27x^{3}+8+54x^{2}-135x=0
    <=>-99x=0
    <=>x=0
    Vậy S={0}
     

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

Thúy Mai

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