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

Toán Lớp 8: a.(x+1)(x-4)–x^2=0 b)(2x-1)(x-3)-2(x+1)^2=0 c)x^2-25–(x+5)=0 d.3x(x-2)–x+2=0 e.x( x–4)=2x -8 f.3x(x+5) –3x–15=0 g.(3x–1)^2 –(x+5)^2=0

Tháng Mười Hai 8, 2022 Toán học 1 Comment 0 views

Toán Lớp 8: a.(x+1)(x-4)–x^2=0
b)(2x-1)(x-3)-2(x+1)^2=0
c)x^2-25–(x+5)=0
d.3x(x-2)–x+2=0
e.x( x–4)=2x -8
f.3x(x+5) –3x–15=0
g.(3x–1)^2 –(x+5)^2=0

Comments ( 1 )

  1. kimnguenoanh
    kimnguenoanh
    8 Tháng Mười Hai, 2022 at 2:03 chiều
    Reply
    Giải đáp:
    Lời giải và giải thích chi tiết:
    a.(x+1)(x-4)-x^2=0
    <=>x^2−4x+x−4-x^2=0
    <=>−3x−4=0
    <=>−3x=4
    <=>x=-4/3
    Vậy x=-4/3
     
    b)(2x-1)(x-3)-2(x+1)^2=0
    <=>2x^2−7x+3−2(x^2+2x+1)=0
    <=>2x^2−7x+3−2x^2-4x-2=0
    <=>−11x+1=0
    <=>−11x=-1
    <=>x=1/11
     
    c)x^2-25-(x+5)=0
    <=>x^2−25−x−5=0
    <=>x^2−x−30=0
    <=>x^2+5x-6x−30=0
    <=>(x^2+5x)-(6x+30)=0
    <=>x(x+5)-6(x+5)=0
    <=>(x+5)(x-6)=0
    ⇔\(\left[ \begin{array}{l}x+5=0⇔x=-5\\x-6=0⇔x=6\end{array} \right.\)
    Vậy x∈{-5;6}
     
    d.3x(x-2)-x+2=0
    <=>3x^2−6x−x+2=0
    <=>3x^2−7x+2=0
    <=>3x^2−6x-x+2=0
    <=>(3x^2−6x)-(x-2)=0
    <=>3x(x−2)-1(x-2)=0
    <=>(x−2)(3x-1)=0
    ⇔\(\left[ \begin{array}{l}x-2=0⇔x=2\\3x-1=0⇔x=\frac{1}{3}\end{array} \right.\)
    Vậy x∈{2;1/3}
     
    e.x(x-4)=2x-8
    <=>x^2−4x−2x+8=0
    <=>x^2−6x+8=0
    <=>x^2−2x-4x+8=0
    <=>x(x−2)-4(x-2)=0
    <=>(x−2)(x-4)=0
    ⇔\(\left[ \begin{array}{l}x-2=0⇔x=2\\x-4=0⇔x=4\end{array} \right.\)
    Vậy x∈{2;4}
     
    f.3x(x+5)-3x-15=0
    <=>3x^2+15x-3x-15=0
    <=>x^2+4x−5=0
    <=>x^2-x+5x−5=0
    <=>(x^2-x)+(5x−5)=0
    <=>x(x-1)+5(x−1)=0
    <=>(x-1)(x+5)=0
    ⇔\(\left[ \begin{array}{l}x-1=0⇔x=1\\x+5=0⇔x=-5\end{array} \right.\)
    Vậy x∈{1;-5}
     
    g.(3x-1)^2-(x+5)^2=0
    <=>9x^2−6x+1−(x^2+10x+25)=0
    <=>9x^2−6x+1−x^2-10x-25=0
    <=>x^2−2x−3=0
    <=>x^2−3x+x−3=0
    <=>(x^2−3x)+(x−3)=0
    <=>x(x−3)+1(x−3)=0
    <=>(x+1)(x−3)=0
    ⇔\(\left[ \begin{array}{l}x+1=0⇔x=-1\\x-3=0⇔x=3\end{array} \right.\)
    Vậy x∈{-1;3}

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

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