Centuries: 1st century - 2nd century - 3rd century
Decades: 80s - 90s - 100s - 110s - 120s - 130s - 140s - 150s - 160s - 170s - 180s
130 131 132 133 134 135 136 137 138 139
Events:
... we must have y = b/(2a), so we add the square of b/(2a) to both sides, ...