已知a是方程x2-3x-1=0的一个根，则2a2-6a+7=______．
人气：374 ℃ 时间：2019-08-21 19:05:29
解答
∵a是x2-3x-1=0的一个根，
∴a2-3a-1=0，
∴a2-3a=1，
∴2a2-6a=2，
∴2a2-6a+7=9，
故答案为：9．
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