(a+b)(a−b)=a2−ab+ab−b2=a2−b2∴[x3−(1x3)]⋅[x3+(1x3)]=[x6−(1x6)]
∴ k=6
A sequence x1,x2,x3,...... is defined by letting x1=2 and xk=xk−1n for all natural numbers k, k≥2. Show that xn=2n! for all nϵN.