\(x^3-\left(x-2\right)\left(x^2+x-2\right)=8\)
\(\Leftrightarrow x^3-8-\left(x-2\right)\left(x^2+x-2\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x^2+2x+4\right)-\left(x-2\right)\left(x^2+x-2\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x^2+2x+4-x^2-x+2\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x+6\right)=0\)
=>x=2 hoặc x=-6
=>a=2; b=-6
=>a/b=-1/3



