题目内容
解方程x2－4x＋1＝0．
解法一：移项，得x2－4x＝－1．··························· 1分
配方，得 x2－4x＋4＝－1＋4，························ 2分
(x－2)2 ＝3．··························· 3分
由此可得 x－2 ＝±
．·························· 4分
x1＝2＋，x2＝2－．·························· 6分
解法二：a＝1，b＝－4，c＝1．
b2－4ac＝(－4)2－4×1×1＝12＞0．······················ 2分
x＝
································· 4分
＝2±．
x1＝2＋，x2＝2－． 6分
∴x＝
＝2±
. ∴x1＝2＋， x2＝2–， ……………6分
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