停电设备的两端，应有明显的断开点，若无法观察到停电设备的断开点，应有能够反映设备运行状态的电气和机械等指示。
错误
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Thosewho’dliketovisittheexhibition________(sign)yournameshere.
heteachertoldthemsincelight________(travel)fasterthansound,lightning________(appear)togobeforethunder.
Applicantsshouldnotethatallpositionsare——toAustraliancitizenshiprequirements．
曲线在点（0，-1）处的切线方程为________.
设二次型f(x1,x2)=x12+4x1x2+4x22经正交变换化为二次型，求ab的值。