2) ( a - b)( 7 - 4(a - b)) = ( a - b)(7 - 4a + 4b)
4) ( x^2 - y^2) + ( x - y) = ( x - y)(x + y) + ( x - y) = ( x - y)(x + y + 1)
6) ( x^2 - 4y^2) - 5(x + 2y) = ( x - 2y)(x + 2y) - 5( x + 2y) = ( x + 2y)(x - 2y - 5)
8) ( 4a^2 - 9b^2) + ( 2a - 3b) = ( 2a - 3b)(2a + 3b) + ( 2a - 3b) =
= ( 2a - 3b)(2a + 3b + 1)