Simply.. 4/(-5-5√5)?
2015-07-26 11:46 pm
The answer is (1-√5)/5 I tried doing it several times but keep on getting a different answer, so please help me. Thanks.
回答 (2)
2015-07-26 11:55 pm
4/(-5 -5√5)
= 4/((-5)(1 +√5)
= -4/5 * 1/(1+√5)
= -4/5 * (1-√5)/((1-√5)(1+√5))
= -4/5 * (1-√5)/(1 - 5)
= -4/5 *(1 - √5)/(-4)
= (1- √5)/5
= 4/((-5)(1 +√5)
= -4/5 * 1/(1+√5)
= -4/5 * (1-√5)/((1-√5)(1+√5))
= -4/5 * (1-√5)/(1 - 5)
= -4/5 *(1 - √5)/(-4)
= (1- √5)/5
2015-07-27 12:33 am
4/(-5-5√5)
4/ [-5(1+√5)]
multiply by (1-√5)/(1-√5) this is a trick to eliminate radicals!
-4/5 * (1-√5)/[(1+√5)(1-√5)]
we know (1+√5)(1-√5) using FOIL is 1 -√5 +√5 -√5√5
or 1 -5 = -4
Now we have
-4/5 * (1-√5)/(-4)
-4/-4 cancels
1/5 * (1-√5)
or (1-√5)/5
4/ [-5(1+√5)]
multiply by (1-√5)/(1-√5) this is a trick to eliminate radicals!
-4/5 * (1-√5)/[(1+√5)(1-√5)]
we know (1+√5)(1-√5) using FOIL is 1 -√5 +√5 -√5√5
or 1 -5 = -4
Now we have
-4/5 * (1-√5)/(-4)
-4/-4 cancels
1/5 * (1-√5)
or (1-√5)/5
收錄日期: 2021-04-21 12:00:54
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20150726154655AAB7thv