$a,x^3+\frac{1}{x^3}=(x+\frac{1}{x})(x^2+\frac{1}{x^2}-1)=a.[(x+\frac{1}{x})^2-2.x.\frac{1}{x}-1]=a.(a^2-2-1)=a(a^2-3)$
$a,x^3+\frac{1}{x^3}=(x+\frac{1}{x})(x^2+\frac{1}{x^2}-1)=a.[(x+\frac{1}{x})^2-2.x.\frac{1}{x}-1)=a.(a^2-2-1)=a(a^2-3)$
$a,x^3+\frac{1}{x^3}=(x+\frac{1}{x})(x^2+\frac{1}{x^2}-1)=a.[(x+\frac{1}{x})^2-2.x.\frac{1}{x}-1
]=a.(a^2-2-1)=a(a^2-3)$