Tìm x , biết :
a) 2.(x+1)-4x=15
b) (x-1).(x+1)-x.(x+4)
d) x mũ 2 – 6x = 9
Giúp tui zớii
Vote 5 sao + ctlhn ạ
Tìm x , biết :
a) 2.(x+1)-4x=15
b) (x-1).(x+1)-x.(x+4)
d) x mũ 2 – 6x = 9
Giúp tui zớii
Vote 5 sao + ctlhn ạ
a) $2(x+1)-4x=15$
$↔2x+2-4x=15$
$↔-2x=13$
$↔x=-\dfrac{13}{2}$
b) $(x-1)(x+1)-x(x+4)$
$=x^2-1-x^2-4x$
$=-1-4x$
c) $x^2-6x=9$
$↔x^2-6x+9-9=0$
$↔(x-3)^2=9$
$\begin{cases}x-3=3\\x-3=-3\end{cases}$
$\begin{cases}x=6\\x=0\end{cases}$