2( x” + 1 ) - 5x
= 2x” + 2 - 5x
= 2x" - 4x - x + 2
= 2x( x - 2 ) - ( x - 2 )
= ( x - 2 )( 2x - 1 )
或者
= 2x” - x - 4x + 2
= x( 2x - 1 ) - 2( 2x - 1 )
= ( x - 2 )( 2x - 1 )