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[求助]a math problem, can someone help me?

dmd216@2003-06-28 08:36

Find the sum of the first one hundred terms in the progression.

(-6, -2, 2, 6.......)

A. 19,200

B. 19,400

C. -604

D. 604

if possible, can anyone tell me the steps? thank you very much.

引用

dmd216@2003-06-28 08:41

another one,

Given the series of examples below, what is 5¢4?
4¢3=13 7¢2=47 3¢1=8 1¢5=-4

A. 20

B. 29

C. 1

D. 21

also, can anyone tell me what this symbol "¢" means? I never see it before. thank you.

引用

Re: [求助]a math problem, can someone help me?

yuetsantse@2003-06-28 10:00

引用
最初由 dmd216 发布
Find the sum of the first one hundred terms in the progression.

(-6, -2, 2, 6.......)

A. 19,200

B. 19,400

C. -604

D. 604

if possible, can anyone tell me the steps? thank you very much.

1st term(t1) = -6
n = 100
d = +4

這是Arithmetic Series, 所以用這公式
Sn = n/2 x [ 2t1 + (n-1)d]

代入去就是．．．
S100=100/2 [2(-6) + (100-1) 4]
答案就是 a) 19,200

但如果不知道d的值, 就用下面的式
Sn = n/2 (t1+tn)

剛剛學過所以才知道-____-

下面的我不會-___-

引用

yuetsantse@2003-06-28 10:16

引用
最初由 dmd216 发布
another one,

Given the series of examples below, what is 5¢4?
4¢3=13 7¢2=47 3¢1=8 1¢5=-4

A. 20

B. 29

C. 1

D. 21

also, can anyone tell me what this symbol "¢" means? I never see it before. thank you.

剛看了一下
雖然不明白¢是什麼
但看到出來...

4¢3=13
4*4-3=13

7¢2=47
7*7-2=47

3¢1=8
3*3-1=8

1¢5=-4
1*1-5=-4

所以, 照推理
5¢4就是
5*5-4
應該是D) 21

但我不知道符號的意思-____-

引用

阿苏@2003-06-28 10:29

引用
最初由 dmd216 发布
another one,

Given the series of examples below, what is 5¢4?
4¢3=13 7¢2=47 3¢1=8 1¢5=-4

A. 20

B. 29

C. 1

D. 21

also, can anyone tell me what this symbol "¢" means? I never see it before. thank you.

13=4*4-3 47=7*7-2 8=3*3-1 -4=1*1-5

5*5-4=21

choose D

:D :D :D :D

引用

Lizard@2003-06-28 10:35

so this symbol"¢" means square??

引用

阿苏@2003-06-28 11:11

no... the question's intention is to let you guess what "¢" means in the equation... here it means take the square...

引用

alex31@2003-06-28 15:51

我只知道¢是金钱单位，和$有100:1的关系

引用

Re: [求助]a math problem, can someone help me?

amous@2003-06-28 17:05

汗...樓主是看不懂英文吧...問題很簡單

引用
最初由 dmd216 发布
Find the sum of the first one hundred terms in the progression.

(-6, -2, 2, 6.......)

A. 19,200

B. 19,400

C. -604

D. 604

if possible, can anyone tell me the steps? thank you very much.