1/a = x+1+1/x x+ 1/x = 1/a -1x² / (x⁴+x²+1)= 1/(x² + 1 + 1/x²)= 1/ [ (x+ 1/x)² -1 ]= 1/ [ (1/a -1)² -1 ]= a² / (1-2a)