Toán Lớp 8: x(x+2)(x+4)(x+6)=9 Tìm x biết:
Leave a reply
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.
Toán Lớp 8: x(x+2)(x+4)(x+6)=9 Tìm x biết:
Comments ( 1 )
$\text{x (x+2) (x+4) (x+6) = 9 }$
$\text{⇔ {x ( x + 6 ) } { ( x + 2 ) ( x + 4 ) } = 9 }$
$\text{⇔ ( x² + 6x ) ( x² + 6x + 8 ) = 9 }$
$\text{Đặt x² + 6x + 4 = t}$
$\text{⇔ ( t – 4 ) ( t + 4 ) = 9 }$
$\text{⇔ t² – 16 – 9 = 0 }$
$\text{⇔ t² – 25 = 0}$
$\text{⇔ t = 5}$
$\text{⇔ x² + 6x + 4 = 5 }$
$\text{⇔ x² + 6x + 9 = 0 }$
$\text{⇔ x² + 6 x – 1 = 0 }$
⇔ \(\left[ \begin{array}{l}(x=3)²=0\\( x = 3 )² – 0 = 0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=-3\\x=-3+ \sqrt{10}\end{array} \right.\)