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:

... quadratic formula is derived by the method of completing the square[?]. <math>ax^2+bx+c=0</math> Dividing our quadratic equation by a, we ...