Question

x⁴-8x-9=0

Answer 1

Ta có: x⁴ - 8x - 9 = 0

=> x⁴ - 8x = 9

=> x(x³ - 8) = 9

\(\Rightarrow\left[{}\begin{matrix}x=9\\x^3-8=9\Rightarrow x^3=17\Rightarrow x=\sqrt[3]{17}\end{matrix}\right.\)

Answer 2

Ơ lộn, cho mik sửa lại:

Ta có: x⁴ - 8x - 9 = 0

=> x⁴ - 8x = 9

=> x(x³ - 8) = 9

=> x(x³ - 2³) = 9

=> x(x - 2)(x² + 2x + 2²) = 9

=> x(x - 2)(x² + 2x + 4) = 9

\(\Rightarrow\left[{}\begin{matrix}x=9\\x-2=9\Rightarrow x=11\\x^2+2x+2^2=9\Rightarrow x^2+2x=5\Rightarrow x\left(x+2\right)=5\Rightarrow\left[{}\begin{matrix}x=5\\x+2=5\Rightarrow x=3\end{matrix}\right.\end{matrix}\right.\)

Answer 3

Ta có: x⁴ - 8x - 9 = 0

=> x⁴ - 8x = 9

=> x(x³ - 8) = 9

=> x(x³ - 2³) = 9

=> x(x - 2)(x² + 2x + 2²) = 9

=> x(x - 2)(x² + 2x + 4) = 9

\(\Rightarrow\left[{}\begin{matrix}x=9\\x-2=9\\x^2+2x+4=9\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=9\\x=11\\x^2+2x=5\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=9\\x=11\\x\left(x+2\right)=5\Rightarrow\left[{}\begin{matrix}x=5\\x+2=5\Rightarrow x=3\end{matrix}\right.\end{matrix}\right.\)

Vậy...

Answer 4

Bài sau mik sợ bn k rõ nên ghi lại rõ hơn rồi nha ;)