已知代数式14x+5-21x平方=-2,求3x²-2x+5的值=
人气：294 ℃ 时间：2019-09-16 22:16:37
解答
解
14x+5-21x²=-2
∴-21x²+14x=-7
两边除以-7得：
3x²-2x=1
∴3x²-2x+5
=1+5
=6
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