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問題: 28( x + y )^2 + 7 ( x - y )^2 請連步驟
最佳解答:
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)
其他解答:
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
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maths 因式分解一問 20分發問:
問題: 28( x + y )^2 + 7 ( x - y )^2 請連步驟
最佳解答:
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)
其他解答:
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
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