Register Now

Login

Lost Password

Lost your password? Please enter your email address. You will receive a link and will create a new password via email.

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

Toán Lớp 8: tìm x x^2-6x-4x+24=0 x^2+3x-2x-6=0 x^2-8x+3x-24=0 x^2-20+x-20=0 x^2+6x-x-6=0 x^2+8x+3x+24=0

Tháng Sáu 14, 2022 Toán học 2 Comments 0 views

Toán Lớp 8: tìm x
x^2-6x-4x+24=0
x^2+3x-2x-6=0
x^2-8x+3x-24=0
x^2-20+x-20=0
x^2+6x-x-6=0
x^2+8x+3x+24=0

Comments ( 2 )

  1. tonhitruc
    tonhitruc
    14 Tháng Sáu, 2022 at 8:32 chiều
    Reply
    a) x^2-6x-4x+24=0
    ⇔(x^2-6x)-(4x-24)=0
    ⇔x(x-6)-4(x-6)=0
    ⇔(x-6)(x-4)=0
    ⇔\(\left[ \begin{array}{l}x-6=0\\x-4=0\end{array} \right.\) 
    ⇔\(\left[ \begin{array}{l}x=6\\x=4\end{array} \right.\) 
    Vậy S={6,4}
    b) x^2+3x-2x-6=0
    ⇔(x^2+3x)-(2x+6)=0
    ⇔x(x+3)-2(x+3)=0
    ⇔(x+3)(x-2)=0
    ⇔\(\left[ \begin{array}{l}x+3=0\\x-2=0\end{array} \right.\) 
    ⇔\(\left[ \begin{array}{l}x=-3\\x=2\end{array} \right.\) 
    Vậy S={-3,2}
    c) x^2-8x+3x-24=0
    ⇔(x^2-8x)+(3x-24)=0
    ⇔x(x-8)+3(x-8)=0
    ⇔(x-8)(x+3)=0
    ⇔\(\left[ \begin{array}{l}x-8=0\\x+3=0\end{array} \right.\) 
    ⇔\(\left[ \begin{array}{l}x=8\\x=-3\end{array} \right.\) 
    Vậy S={8,-3}
    d) x^2-20+x-20=0
    ⇔x^2+x-40=0
    ⇔(x^2+2.x.(1)/(2)+1/4)-40-1/4=0
    ⇔(x-1/2)^2-(161)/(4)=0
    ⇔(x-1/2)^2=(161)/(4)
    ⇔\(\left[ \begin{array}{l}x-\dfrac{1}{2}=\sqrt{\dfrac{161}{4}}\\x-\dfrac{1}{2}=-\sqrt{\dfrac{161}{4}}\end{array} \right.\) 
    ⇔\(\left[ \begin{array}{l}x=\dfrac{1+\sqrt{161}}{2}\\x=\dfrac{1-\sqrt{161}}{2}\end{array} \right.\)  
    Vậy S={(1+\sqrt{161})/(2),(1-\sqrt{161})/(2)}
    e) x^2+6x-x-6=0
    ⇔(x^2+6x)-(x+6)=0
    ⇔x(x+6)-(x+6)=0
    ⇔(x+6)(x-1)=0
    ⇔\(\left[ \begin{array}{l}x+6=0\\x-1=0\end{array} \right.\) 
    ⇔\(\left[ \begin{array}{l}x=-6\\x=1\end{array} \right.\) 
    Vậy S={-6,1}
    f) x^2+8x+3x+24=0
    ⇔(x^2+8x)+(3x+24)=0
    ⇔x(x+8)+3(x+8)=0
    ⇔(x+8)(x+3)=0
    ⇔\(\left[ \begin{array}{l}x+8=0\\x+3=0\end{array} \right.\) 
    ⇔\(\left[ \begin{array}{l}x=-8\\x=-3\end{array} \right.\) 
    Vậy S={-8,-3}

  2. maingoctruc
    maingoctruc
    14 Tháng Sáu, 2022 at 8:32 chiều
    Reply
    $\\$
    Giải đáp + giải thích các bước giải :
    a,
    x^2 – 6x-4x+24=0
    ->(x^2-6x)-(4x-24)=0
    ->x(x-6)-4(x-6)=0
    ->(x-6)(x-4)=0
    ->x-6=0 hoặc x-4=0
    ->x=6 hoặc x=4
    Vậy x=6,x=4
    b,
    x^2 +3x-2x-6=0
    ->(x^2+3x)-(2x+6)=0
    ->x(x+3)-2(x+3)=0
    ->(x+3)(x-2)=0
    ->x+3=0 hoặc x-2=0
    ->x=-3 hoặc x=2
    Vậy x=-3,x=2
    c,
    x^2 – 8x + 3x-24=0
    ->(x^2-8x)+(3x-24)=0
    ->x(x-8)+3(x-8)=0
    ->(x-8)(x+3)=0
    ->x-8=0 hoặc x+3=0
    ->x=8 hoặc x=-3
    Vây x=8,x=-3
    d,
    x^2-20+x-20=0
    ->x^2+x-40=0
    ->x^2+2.x. 1/2 + (1/2)^2 -161/4=0
    ->(x+1/2)^2=161/4
    TH1 :
    x+1/2=\sqrt{161/4}
    ->x=(-1+\sqrt{161})/2
    TH2 :
    x+1/2=-\sqrt{161/4}
    ->x=-(1+\sqrt{161})/2
    Vậy x=(-1+\sqrt{161})/2, x=-(1+\sqrt{161})/2
    e,
    x^2+6x-x-6=0
    ->(x^2+6x)-(x+6)=0
    ->x(x+6)-(x+6)=0
    ->(x+6)(x-1)=0
    ->x+6=0 hoặc x-1=0
    ->x=-6 hoặc x=1
    Vậy x=-6,x=1
    f,
    x^2+8x+3x+24=0
    ->(x^2+8x)+(3x+24)=0
    ->x(x+8)+3(x+8)=0
    ->(x+8)(x+3)=0
    ->x+8=0 hoặc x+3=0
    ->x=-8 hoặc x=-3
    Vậy x=-8,x=-3

Leave a reply

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

An Kim

About An Kim