单项选择题
A.∣A+B∣=∣A∣+∣B∣B.∣AB∣=∣A∣∣B’∣C.∣AB-1∣=∣A∣∣B∣D.∣kA∣=k∣A∣
A.已知方差,检验均值B.未知方差,检验均值C.已知均值,检验方差D.未知均值,检验方差
A.B.x1+x4-2μC.D.