wisdoman 發表於 7-11-2008 08:10:14

Taking square roots

If x2 = 49
x = ± 7
But if x=√100
then
x=10


我想問sq.rt. 100 點解唔係± 10 ge...

sing2 發表於 7-11-2008 17:35:15

原帖由 wisdoman 於 7-11-2008 08:10 發表 http://www.nakuz.com/bbs/images/common/back.gif
If x2 = 49
x = ± 7
But if x=√100
then
x=10


我想問sq.rt. 100 點解唔係± 10 ge...
我諗應該係你
x^2=49
所以先要
   x=±7
而你一開始就係
x=√100
就唔需要±
p.s 我的愚見

-終場ソ使者- 發表於 7-11-2008 17:54:47

√100=±10
冇人話=+10 only- -

wilson1993912 發表於 7-11-2008 18:07:27

我想問sq.rt. 100 點解唔係± 10 ge...

因為你計錯-.-

wisdoman 發表於 7-11-2008 18:54:06

原帖由 -終場ソ使者- 於 7-11-2008 17:54 發表
√100=±10
冇人話=+10 only- -

原帖由 wilson1993912 於 7-11-2008 18:07 發表 http://www4.nakuz.com/bbs/images/common/back.gif
我想問sq.rt. 100 點解唔係± 10 ge...

因為你計錯-.-

you mean √100=± 10 ?[] can you explain...

-終場ソ使者- 發表於 7-11-2008 19:44:38

(-10)^2=100
(+10)^2=100
咁sqt100就係=+/-10

Zend 發表於 7-11-2008 20:09:21

sqrt 100 = 10 only
我發現好多人9 up =.=...

lkhj2525 發表於 7-11-2008 20:36:11

原帖由 -終場ソ使者- 於 7-11-2008 11:44 發表 http://www.nakuz.com/bbs/images/common/back.gif
(-10)^2=100
(+10)^2=100
咁sqt100就係=+/-10
√100 = 10
√-100 = √(-1)√(100) = 10i   ,i is a imaginary number which is learned in F.6~7
所以 √100 不會等於負數

[ 本帖最後由 lkhj2525 於 7-11-2008 12:47 編輯 ]

-終場ソ使者- 發表於 7-11-2008 20:40:53

咁sqrt49都得姐

Zend 發表於 7-11-2008 20:48:43

also the same =.=
in fact, this is a common mistake made by students []
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