Question

Tìm x:

x³+27+(x+3)(x-9)=0

Answer 1

x=-3

________
_________
ks với

Answer 2

làm hẳn ra bạn

Answer 3

\(x^3+27+\left(x+3\right)\left(x-9\right)=0\)

\(x^3+3^3+\left(x+3\right)\left(x-9\right)=0\)

\(\left(x+3\right)\left(x^2-3x+9\right)+\left(x+3\right)\left(x-9\right)=0\)

\(\left(x+3\right)\left(x^2-3x+9+x-9\right)=0\)

\(\left(x+3\right)\left(x^2-2x\right)=0\)

\(x\left(x+3\right)\left(x-2\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x+3=0\end{cases}ho\text{ặc}}x-2=0\)

\(\Leftrightarrow\orbr{\begin{cases}x=0\\x=-3\end{cases}ho\text{ặc}}x=2\)

Vậy \(\orbr{\begin{cases}x=0\\x=-3\end{cases}ho\text{ặc}}x=2\)