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.下面给出四种说法： ①设a、b、c分别表示数据15、17、14、10、15、17、17、16、14、12的平均数、中位数、众数，则a＜b＜c； ②在线性回归模型中，相关指数R 2 表示解释变量对于预报变量变化的贡献率，R 2 越接近于1，表示回归的效果越好 ③绘制频率分布直方图时，各小长方形的面积等于相应各组的组距； ④设随机变量ξ服从正态分布N（4，2 2 ），则P（ξ＞4）= 1 2 ． 其中正确的说法有______（请将你认为正确的说法的序号全部填写在横线上）
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举一反三
【单选题】His sufferings are largely _______ his putting a false value on things.
A.
about to
B.
because of
C.
due to
D.
owe to
【简答题】In the text, the sufferings of the poor are descnbed as _______ . [ A] one misfortune leading to another [ B ] being the result of unemployment [ C] caused by the lack of social care [ D ] becoming mo...
【单选题】The war and the sufferings that it caused ______.
A.
affected him greatly
B.
changed his writing
C.
made him very brave
D.
pred his writing
【简答题】A={x|x 2 -3x+2='0}' B={x|ax=1},B包含于A，求a值
【简答题】试求x'=Ax+f(t)，其中 ， 满足初值条件 的解φ(t)．
【简答题】__, they forgot their bitter sufferings. 求翻译，谢谢！
【简答题】φ(0)=0， ， . 试求方程组x'=Ax+f(t)的解φ(t)：
【单选题】Which of the following is TRUE?
A.
The sufferings of eider females have been ignored for a long time.
B.
Old women's special role in society has been underestimated.
C.
Paternal grandmothers are equally important for a child as maternal ones.
D.
There are low proportions of older s among 'primitive' cultures.
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