( x" - 1 )" + 6( 1 - x" ) + 9
= ( x" - 1 )" - 2X 3( x" - 1 ) + 3"
= ( x" - 1 - 3 )"
= ( x" - 4 )"
= ( x + 2 )"( x - 2 )"
或者
= ( 1 - x" )" + 2X 3( 1 - x" ) + 3"
= ( 1 - x" + 3 )"
= ( 4 - x" )"
= ( 2 - x )"( 2 + x )"
= ( x - 2 )"( x + 2 )"