Упростите выражение:

(n+1) (2n-3) + (n-1) (3n+1)

(x-y) (2x-3y) - (3x-y) (2x+y)

(2a+3) (2a+3) - (2a+1) (2a-1)

(3c-d) (d+3c) + (4c-d) (c-4d)

1) (2n²-3n+2n-3) + (3n²+n-3n-1) = 5n²-3n-4

2) (2x²-3xy-2xy+3y²) - (6x²+3xy-2xy-y²) = 4y²-4x²-6xy=2 (2y²-2x²-3xy)

3) (4a²+6a+6a+9) - (4a²-2a+2a-1) = 12a+10=2 (6a+5)

4) (3cd+9c²-d²-3cd) + (4c²-16cd-cd+4d²) = 13c²-17cd+d²