快快快,1小時內!!!20分!!!

1) 用十字相乘法,

x^2 - 9

x^2 - 1

---------------

-9x^2 - x^2 = -10x^2

所以x^4 - 10x^2 + 9

= ( x^2 - 9 )( x^2 - 1 )

= ( x + 3 )( x - 3 )( x + 1 )( x - 1 ) [ 用恆等式a^2 - b^2 = ( a + b )( a - b )]

(x^2 - 1)( x^-9) 囉!!
好易姐~"~

(x^2 - 1)( x^-9)