a, \(3x^2-3y^2\)
\(\Leftrightarrow3\left(x^2-y^2\right)\)
\(\Leftrightarrow3\left(x-y\right)\left(x+y\right)\)
b,\(x^4-y^4\)
\(\Leftrightarrow\left(x^2-y^2\right)\left(x^2+y^2\right)\)
\(\Leftrightarrow\left(x-y\right)\left(x+y\right)\left(x^2+y^2\right)\)
c,\(x^4-8x\)
\(\Rightarrow x\left(x^3-8\right)\)
\(\Rightarrow x\left(x-2\right)\left(x^2+2x+4\right)\)