chọn tiếp giúp nha mk cho 5 sao

Đáp án:

 $13):$

$2.(x+4)+x.(x+4)$

$= (2+x).(x+4)$

$⇒C$

$14):$

$1-3x+3x²-x³$

$= 1³-3.1².x+3.1.x²-x³$

$= (1-x)³$

$+)Thay$ $x=2$ $vào$ $bt$ $trên$ $ta$ $đc:$

$→ (1-2)³=(-1)³=-1$

$Vậy$ $giá$ $trị$ $của$ $bt$ $trên$ $khi$ $x=2$ $là$ $-1$ 

$⇒C$

$15):$

$x.(x-1)+2.(x-1)=0$

$⇔ (x+2).(x-1)=0$

$⇔$ \(\left[ \begin{array}{l}x+2=0\\x-1=0\end{array} \right.\) $⇔$ \(\left[ \begin{array}{l}x=-2\\x=1\end{array} \right.\)

$Vậy$ $x=-2$ $hoặc$ $x=1$ 

$⇒A$

$16):$

$ x-4²=0$

$⇔ x-16=0$

$⇔ x=16$

$Vậy$ $x=16$

$⇒C$