Question

Tìm x biết \(\left(4x+3\right)^3+\left(5-7x\right)^3+\left(3x-8\right)^3=0\)

Answer 1

\(Dat:\left\{{}\begin{matrix}4x+3=a\\3x-8=b\end{matrix}\right.\Rightarrow-4x-3+8-3x=5-7x=-a-b\Rightarrow a^3-\left(a+b\right)^3+b^3=0\Leftrightarrow-3ab\left(a+b\right)=0\Leftrightarrow\left[{}\begin{matrix}a=0\\b=0\\a+b=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}4x+3=0\\3x-8=0\\5-7x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{-3}{4}\\x=\frac{8}{3}\\x=\frac{5}{7}\end{matrix}\right.\)