問題: 28( x + y )^2 + 7 ( x - y )^2
請連步驟
maths 因式分解一問 20分
2009-01-14 3:01 am
回答 (2)
2009-01-14 5:00 am
✔ 最佳答案
28( x + y )2 + 7 ( x - y )2=7[(x+y)2+(x-y)2]
=7[(x+y)+(x-y)][(x+y)-(x-y)]
=7(2x)(2y)
=28xy
2009-01-23 20:42:44 補充：
唔好意思,錯左
28( x + y )^2 + 7 ( x - y )^2
=7[4(x+y)^2+(x-y)^2]
=7[(4(x^2+2xy+y^2)+(x^2-2xy+y^2)]
=7(5x^2+6xy+5y^2)
2009-01-14 5:08 am
28( x + y )^2 + 7 ( x - y )^2
= 28 ( x + y )( x + y )+ 7 ( x - y )( x - y )
= 28 ( x^2 + 2xy + y^2 )+ 7 ( x^2 - 2xy + y^2 )
= 28x^2 + 56xy + 28y^2+ 7x^2 - 14xy+ 7y^2
= 28x^2 + 7x^2 + 28y^2 + 7y^2 + 56xy - 14xy
= 35x^2 + 35y^2 + 42xy
= 28 ( x + y )( x + y )+ 7 ( x - y )( x - y )
= 28 ( x^2 + 2xy + y^2 )+ 7 ( x^2 - 2xy + y^2 )
= 28x^2 + 56xy + 28y^2+ 7x^2 - 14xy+ 7y^2
= 28x^2 + 7x^2 + 28y^2 + 7y^2 + 56xy - 14xy
= 35x^2 + 35y^2 + 42xy
參考: myself
收錄日期: 2021-04-20 11:47:08
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20090113000051KK01366