Question

1.tìm x

(x+2)(x²-2x+4)+(x+2)²=00

2.tính giá trị biểu thức

9x⁴-15x³-6x²+55 biết 3x²-5x=2

Answer 1

\(1,\left(x+2\right)\left(x^2-2x+4\right)+\left(x+2\right)^2=0\)

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

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

\(\Rightarrow\left[{}\begin{matrix}\left(x+2\right)^2=0\\x+3=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x+2=0\\x+3=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=-2\\x=-3\end{matrix}\right.\)

Vậy....