4(a-b)^3-12(b-a)^2
我知個答案係4(a-b)^2(a-b-3)
點解係-3而唔係+3 ?
唔該可唔可以講哂d步驟比我聽牙
真係好唔明 =-=
唔該教教我
萬分感謝 =]
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3(x-y)-6a(y-x)
個答案係3(x-y)(1+2a)
點解係1+2a而唔係1-2a
唔該列個步驟出黎 =]
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謝謝!!
中二數學 唔該
2007-09-09 9:30 pm
回答 (3)
2007-09-09 10:01 pm
✔ 最佳答案
4(a-b)^3-12(b-a)^2=4(a-b)^3 - 12(a-b)^2 (as (b-a)^2=(a-b)^2)
=4(a-b)^2 * [a-b-3]
+3 is wrong because if you consider x^2 ,no matter x is positive/ negative, the sign(正負號) of the expression x^2 is positive.So, assume that a-b=x,
(b-a)^2=[-(a-b)^2]=(a-b)^2
i.e. (-x)^2=x^2
3(x-y)-6a(y-x)
=3(x-y)+6a(x-y)
=(6a+3)(x-y)
=3(x-y)(1+2a)
As y-x=-(x-y), then -6a(y-x)=-[-6a(x-y)]=6a(x-y)
參考: Maths. Knowledge
2007-09-09 10:04 pm
第一個
4(a-b)^3-12(b-a)^2
=4(a-b)^3-12(a-b)^2 <---因為係square,所以a b對調冇變化
=4(a-b)^2(a-b-3)
第二個
3(x-y)-6a(y-x)
=3(x-y)-6a(-x+y)
=3(x-y)+6a(x-y) <---抽負
=3(x-y)(1+2a)
4(a-b)^3-12(b-a)^2
=4(a-b)^3-12(a-b)^2 <---因為係square,所以a b對調冇變化
=4(a-b)^2(a-b-3)
第二個
3(x-y)-6a(y-x)
=3(x-y)-6a(-x+y)
=3(x-y)+6a(x-y) <---抽負
=3(x-y)(1+2a)
參考: me
2007-09-09 9:53 pm
4(a-b)^3-12(b-a)^2
= 4(a-b))^3-[-12(b-a)])^2
=4(a-b)^3+12(a-b)^2
=4(a-b)^2(a+b+3)
3(x-y)-6a(y-x)
=3(x-y)-[-6a(y-x)]
=3(x-y)+6a(x-y)
=3(x-y)(1+2a)
= 4(a-b))^3-[-12(b-a)])^2
=4(a-b)^3+12(a-b)^2
=4(a-b)^2(a+b+3)
3(x-y)-6a(y-x)
=3(x-y)-[-6a(y-x)]
=3(x-y)+6a(x-y)
=3(x-y)(1+2a)
參考: myself
收錄日期: 2021-04-13 13:23:54
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070909000051KK01921