Decades: 1160s 1170s 1180s 1190s 1200s - 1210s - 1220s 1230s 1240s 1250s 1260s
Years: 1207 1208 1209 1210 1211 - 1212 - 1213 1214 1215 1216 1217
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... there are two different solutions x, both of which are real. (Geometrically, this means that the parabola intersects the x-axis in two points.) If the discriminant is ...