Himpunan penyelesaian dri persamaan kuadrat 2x²+5x+5=0 adalah

2x²+5x+5=0
x² + (5/2)x + 5/2 = 0
(x + 5/4)² – 25/16 + 5/2 = 0
(x + 5/4)² – 25/16 + 40/16 = 0
(x + 5/4)² + 15/16 = 0
(x + 5/4)² = -15/16
x + 5/4 = (√-15)/4 atau x + 5/4 = -(√-15)/4
x + 5/4 = (i√15)/4 atau x + 5/4 = (-i√15)/4
x = (i√15 – 5)/4 atau x = (-5 – i√15)/4