X³－9X＋8= X³-1－9X＋9=(X-1)(X²+X+1)-9(X-1)=(X-1)(X²+X-8)=(X-1)(X+1/2+✔33/2)(X+1/2-✔33/2)
x^3-x^2+x^2-9x+8=x^2(x-1)+(x-8)(x-1)=(x-1)(x^2+x-8)
