A) (x + 3 ) ( 4 + x ) = x ( 4 + x ) + 3 ( 4 + x ) = 4x + x² + 12 + 3x = x² + 7x + 12
B) ( y - 5 ) ( y + 2 ) = y ( y + 2 ) - 5 ( y + 2 ) = y² + 2y - 5y - 10= y² - 3y - 10
C) ( a - 7 ) ( 6 - a ) = a ( 6 - a ) - 7 ( 6 - a ) = 6a -a² - 42 + 7a = - a² + 13a - 42
D) ( x + 7 ) ( x - 1 ) = x ( x - 1) + 7 ( x - 1 ) = x² - x + 7x - 7= x² + 6x - 7
