Polynomial analysis into multiplication and find x :

\(x^3-x^2+x-1=0\)

\(x\left(x^2-16\right)-2\left(x^2-16\right)=0\)

For \(A=a^2+b^2+c^2\) where a , b are two consecutive natural numbers , c = ab . Prove that \(\sqrt{A}\) is an odd natural number.