a: \(f\left(x\right)+g\left(x\right)=x^3-3x^2+6x-8+x^3-6x^2+12x-8\)
\(=2x^3-9x^2+18x-16\)
b: \(f\left(1\right)=1^3-3\cdot1^2+6\cdot1-8=1-3+6-8=-2+6-8=4-8=-4\)
\(g\left(-1\right)=-6\cdot\left(-1\right)^2+\left(-1\right)^3-8+12\cdot\left(-1\right)\)
\(=-6\cdot1-1-8-12\)
=-6-21
=-27
c: f(x)-g(x)=0
=>f(x)=g(x)
\(\Leftrightarrow x^3-3x^2+6x-8=x^3-6x^2+12x-8\)
\(\Leftrightarrow3x^2-6x=0\)
=>3x(x-2)=0
=>x=0 hoặc x=2