初中数学题（整式的加减）

(m+2n）-（m-2n）
=m+2n-m+2n
=4n
(2ab+5a²-2b²）-（a²+2ab-2b²)
=2ab+5a²-2b²-a²-2ab+2b²
=4a²
2x-3（x-2y+3z)+2（3x-3y+2z）
=2x-3x+6y-9z+6x-6y+4z
=5x-5z
8m²-[4m²-2m-（2m²-5m）]
=8m²-[4m²-2m-2m²+5m]
=8m ²-[2m²+3m]
=6m²-3m