a)
x³ - 4xy + x²
= x ( x² - 4 y + x )
b)
3 ( x + 2 )- 7y ( x + 2 )
= ( x + 2 ) . ( 3 - 7y )
c) x ( x - 2021 ) - 2021 + x
= x ( x - 2021 ) - (2021 - x)
= (2021 - x ) ( -x - 1 )
d) ( x - 3 ) ² + 4 ( x - 3 )
= ( x - 3 ) . ( x - 3 ) + 4x - 12
= x² - 3x - 3x - 9 + 4x -12
= x² + 4x - 3