# 查看完整版本 : Marix Determinamt + Vectors

## Marix Determinamt + Vectors

Question
[IMG]http://i1382.photobucket.com/albums/ah257/jeffreytam01/IMAG0775_zpsdwnhghxv.jpg[/IMG]
Solution
[IMG]http://i1382.photobucket.com/albums/ah257/jeffreytam01/IMAG0778_zpsbxiwxyjw.jpg[/IMG]
[IMG]http://i1382.photobucket.com/albums/ah257/jeffreytam01/IMAG0781_zpshef2ikvj.jpg[/IMG]
[IMG]http://i1382.photobucket.com/albums/ah257/jeffreytam01/IMAG0780_zpsx3ifhpl1.jpg[/IMG]

14c14c 2015-8-18 08:11 PM

d計算好煩, 唔係太想去對, 淨係講我睇到錯果d
q1a 佢叫你搵determinant

q2 第二行應該係+3 x|...| - (t+3) x|...|

[[i] 本帖最後由 14c14c 於 2015-8-18 08:29 PM 編輯 [/i]]

[quote]原帖由 [i]14c14c[/i] 於 2015-8-18 08:11 PM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=423838250&ptid=25006964][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]
d計算好煩, 唔係太想去對, 淨係講我睇到錯果d
q1a 佢叫你搵determinant

Okay.  I got the same answer 1a as a1b.

For q2, I dont think I did it wrong. Because when you decide the sign (+/-), you use the formula (-1)^1+n where n is the nth row/column. So in this case n=4, the sign should be + for the first one, so -3, and then altering between + and -, so +(t+3). Am I wrong?

Patchouli.K 2015-8-19 03:27 PM

Q1a 既row3 colume3 應該係1+i

Q1b冇錯

Q2點解唔做左Row operation先?
R4+R1 & R3+R2, Det全部用第一個Colume, 咁你條式就係Diagonal上面既野乘埋,

Q3
Vector PQ 係{2,4,6}先岩, 後面錯晒唔洗睇XD

[quote]原帖由 [i]Patchouli.K[/i] 於 2015-8-19 03:27 PM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=423891901&ptid=25006964][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]
Q1a 既row3 colume3 應該係1+i

Q1b冇錯

Q2點解唔做左Row operation先?
R4+R1 & R3+R2, Det全部用第一個Colume, 咁你條式就係Diagonal上面既野乘埋,

Q3
Vec ... [/quote]
Q1a, I dont get what you mean. I cant see any error. Bear in mind that I did some row operations like R1X(1/i), so I need to multiply the invest by the final determinant to get det(M)=-1+i

Q3a Thanks for pointing out the mistake!
So, Dot Product= 24 and Cross Product= (28,-16,20), right?

Q3b, What's wrong? PQ has no effect on it, i guess.

Q3c, 6sqroot(10)?

[[i] 本帖最後由 好男仔 於 2015-8-19 06:34 PM 編輯 [/i]]

14c14c 2015-8-19 08:40 PM

[quote]原帖由 [i]好男仔[/i] 於 2015-8-19 11:27 AM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=423877760&ptid=25006964][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]

Okay.  I got the same answer 1a as a1b.

For q2, I dont think I did it wrong. Because when you decide the sign (+/-), you use the formula (-1)^1+n where n is the nth row/column. So in this case n= ... [/quote]

Patchouli.K 2015-8-20 02:37 AM

[quote]原帖由 [i]好男仔[/i] 於 2015-8-19 06:18 PM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=423902344&ptid=25006964][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]

Q1a, I dont get what you mean. I cant see any error. Bear in mind that I did some row operations like R1X(1/i), so I need to multiply the invest by the final determinant to get det(M)=-1+i

Q3a Th ... [/quote]
Q1a：冇留意到, 咁應該冇錯

Q2：Dot Product= 24 and Cross Product= (28,-16,20) 冇錯

Q3b：因為a錯左所以冇睇ww b part冇錯

Q3c：6Sqrt[10] 冇錯

[quote]原帖由 [i]14c14c[/i] 於 2015-8-19 08:40 PM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=423910404&ptid=25006964][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]

No worries la.
You helped me a lot:smile_o12:Thanks

[quote]原帖由 [i]Patchouli.K[/i] 於 2015-8-20 02:37 AM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=423930141&ptid=25006964][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]

Q1a：冇留意到, 咁應該冇錯

Q2：Dot Product= 24 and Cross Product= (28,-16,20) 冇錯

Q3b：因為a錯左所以冇睇ww b part冇錯

Q3c：6Sqrt[10] 冇錯 [/quote]
Great!
Thanks  for purposely singing up and answering my question!!