\(x^3\left(x^2-7\right)^2-36x\)
\(=x.\left[x^2.\left(x^2-7\right)^2-36\right]\)
\(=x.\left[\left(x^3-7x\right)^2-6^2\right]\)
\(=x.\left(x^3-7x-6\right).\left(x^3-7x+6\right)\)
\(=x.\left(x+1\right)\left(x^2-x-6\right).\left(x-1\right).\left(x^2+x-6\right)\)
\(=x.\left(x+1\right).\left(x+2\right).\left(x+3\right).\left(x-1\right).\left(x-2\right).\left(x-3\right)\)
Ta có : \(x^3\left(x^2-7\right)^2-36x\)
= \(x^3\left(x^4-14x^2+49\right)-36x\)
= \(x\left(x^6-14x^4+49x^2-36\right)\)
= \(x\left(x^2-1\right)\left(x^2-4\right)\left(x^2-9\right)\)---- chỗ này tắt
= (x-3)(x-2)(x-1)x(x+1)(x+2)(x+3)
\(x\left(x^2\left(x^2-7\right)^2-6^2\right)=x\left(x^3-7-6\right)\left(x^3-7+6\right)=x\left(x^3-13\right)\left(x^3-1\right)\)
