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: 1) x^2 + 6 = 2x + x(x-8) 2) x(x-6) – 4x + 24 = 0 3) x^3 – 8 – 2x(x-2) =0 (đề bài là tìm x ạ )

Toán Lớp 8: 1) x^2 + 6 = 2x + x(x-8)
2) x(x-6) – 4x + 24 = 0
3) x^3 – 8 – 2x(x-2) =0 (đề bài là tìm x ạ )

Comments ( 2 )

  1. Giải đáp:
    $1) x^2+6=2x+x.(x-8)$
    $⇔ x²+6=2x+x^2-8x$
    $⇔ x²+6-2x-x^2+8x=0$
    $⇔ (x^2-x^2)+(8x-2x)+6=0$
    $⇔ 6x+6=0$
    $⇔ 6x=-6$
    $⇔ x=-1$
    $vậy$ $x=-1$
    $2) x.(x-6)-4x+24=0$
    $⇔ x.(x-6)-4.(x-6)=0$
    $⇔ (x-4).(x-6)=0$
    $⇔$\(\left[ \begin{array}{l}x-4=0\\x-6=0\end{array} \right.\) $⇔$ \(\left[ \begin{array}{l}x=4\\x=6\end{array} \right.\) 
    $\text{Vậy x ∈ {4;6}}$
    $c) x^3-8-2x.(x-2)=0$
    $⇔ (x-2).(x^2+2x+4)-2x.(x-2)=0$
    $⇔ (x-2).(x^2+2x+4-2x)=0$
    $⇔ (x-2).(x²+4)=0$
    $⇔$ \(\left[ \begin{array}{l}x-2=0\\x^2+4=0\end{array} \right.\) $⇔$ \(\left[ \begin{array}{l}x=2\\x^2=-4 (Vô lí)\end{array} \right.\) 
    $⇔ x=2$
    $vậy$ $x=2$
     

  2. Giải đáp + Lời giải và giải thích chi tiết:
     1)
    x²+6=2x+x(x-8)
    ⇔ x²+6=2x+x²-8x
    ⇔ x²+6-2x-x²+8x=0
    ⇔ 6x+6=0
    ⇔ 6x=-6
    ⇔ x=-1
    Vậy x=-1
    2)
    x(x-6)-4x+24=0
    ⇔ x(x-6)-4(x-6)=0
    ⇔ (x-6)(x-4)=0
    ⇔ $\left[\begin{matrix} x-6=0\\ x-4=0\end{matrix}\right.$
    ⇔ $\left[\begin{matrix} x=6\\ x=4\end{matrix}\right.$
    Vậy x=6 hoặc x=4
    3)
    x³-8-2x(x-2)=0
    ⇔ (x-2)(x²+2x+4)-2x(x-2)=0
    ⇔ (x-2)(x²+2x+4-2x)=0
    ⇔ (x-2)(x²+4)=0
    ⇔ $\left[\begin{matrix} x-2=0\\ x²+4=0\end{matrix}\right.$
    ⇔ $\left[\begin{matrix} x=2\\ x²=-4\text{(vô lí vì x² ≥ 0)}\end{matrix}\right.$
    Vậy x=2

Leave a reply

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

About Thanh Tú