7x^-17x-12=0

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2 | 2009-8-22 17:37:59 | 显示全部楼层 |阅读模式

解：7x^2 -17x-12=0即：x^2 -17x/7 -12/7=0可化为：[x^2 -17x/7+ (17/14)^2] =12/7 +(17/14)^2即：(x -17/14)^2 =336/196 + 289/196得：(x -17/14)^2 =625/196两边同时开方后，得：x -17/14=± 25/14所以：x-17/14=25/14,即：x=17/14 +25/14=42/14=3或x-17/14= -25/14,即：x=17/14 -25/14= -8/14= -4/7...

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