Decades: 1200s 1210s 1220s 1230s 1240s - 1250s - 1260s 1270s 1280s 1290s 1300s
Years: 1251 1252 1253 1254 1255 - 1256 - 1257 1258 1259 1260 1261
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... to <math>x^2+\frac{b}{a}x=-\frac{c}{a}.</math> The equation is now in a form in which we can conveniently complete the square[?]. To "complete the square" ...