We know that,
a3 - b3 = ( a - b )( a2 + ab + b2 ) .....(1)
8a3- b3- 4ax + 2bx
= [ (2a)3 - (b)3 ] - 2 x ( 2a - b )
= ( 2a - b )[ (2a)2 + 2a x b + (b)2 ] - 2 x ( 2a - b ) [ From(1) ]
= ( 2a - b )[ 4a2 + 2ab + b2 ] - 2 x ( 2a - b )
= ( 2a - b )[ 4a2 + 2ab + b2 - 2x ]
