PP3-1(27,84,90)

[william0904]

27.If a certain sample of data has a mean of 20.0 and a standard deviation of 3.0, which of the following values is more than 2.5 standard deviations from the mean?

a.12.0
b.13.5
c.17.0
d.23.5
e.26.5

ANS:A

84.in the arithmetic sequence t1,t2,t3....,tn,..., tn=tn-1-3 for each n.1. What is the value of n when tn=-4?

a.-1
b.7
c.10
d.14
e.20

ANS:C

For which of the following functions f is f(x)=f(1-x) for all x?
a.f(x)=1-x
b.f(x)=1-x^2
c.f(x)=x^2-(1-x)^2
d.f(x)=x^2(1-x)^2
e.f(x)=x/1-x

ANS:D

請問這3題要怎算啊
救救我

[yummysteve]

第一題
3*2.5=7.5
mean=20
20-7.5=12.5
20+7.5=27.5
so A沒有在這範圍裡

第二題題目沒有完全吧
for each n.1 --->這什麼意思

第三題
帶入法帶進去算
哪一個戴X和X-1的值一樣
你帶帶看就知道

[gemstone]

抱歉84是我打錯了
更正:
84.in the arithmetic sequence t1,t2,t3....,tn,..., tn=tn-1-3 for each n.1. What is the value of n when tn=-4?

a.-1
b.7
c.10
d.14
e.20

ANS:C


最後一題裡您說的帶入法是用選項去帶嗎?
感覺怪怪的...