\(a,x^7+x^5+1\)
\(=x^7+x^5+1-x^3+x^3-x^6+x^6+x^2-x^2\)
\(b,\left(x-3\right)\left(x-1\right)\left(x+1\right)\left(x+3\right)\) ( Biểu thức này đã phân tích)
\(=\left[\left(x-3\right)\left(x+3\right)\right]\left[\left(x-1\right)\left(x+1\right)\right]\)
\(=\left(x^2-9\right)\left(x^2-1\right)\)
\(=x^4-10x^2+9\)
\(=x^4-x^2-9x^2+9\)
\(=\left(x^4-x^2\right)-\left(9x^2-9\right)\)
\(=x^2\left(x^2-1\right)-9\left(x^2-1\right)\)
\(=\left(x^2-1\right)\left(x^2-9\right)\)