Decades: 1150s 1160s 1170s 1180s 1190s - 1200s - 1210s 1220s 1230s 1240s 1250s
Years: 1197 1198 1199 1200 1201 - 1202 - 1203 1204 1205 1206 1207
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... = b/(2a), so we add the square of b/(2a) to both sides, getting <math>x^2+\frac{b}{a}x+\frac{b^2}{4a^2}=-\frac{c}{a}+\frac{b^2}{4a^2}.</math> The left ...