Question

Tìm x

a:x³+6x²+9x=0

b:x³-5x²-9x+45

Answer 1

\(x^3+6x^2+9x=0\)

\(x\left(x^2+6x+9\right)=0\)

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

\(\Rightarrow\hept{\begin{cases}x=0\\x=-3\end{cases}}\)

Answer 2

x³-5x²-9x+45=0

=>(x³-5x²)-(9x-45)=0

=>x²(x-5)-9(x-5)=0

=>(x²-9)(x-5)=0

=>x²-9=0  =>x²=9  => x=3;-3

     x-5=0  =>x=5