simplify the rational algebraic expression
1. m²-n²/m³+n³
2. x-2/2x+4
3. 2x+3/(3+2x)
4. -x+4/x-4
5. 3b²-a/3a - b²
6. 3b²-a/-3a-b²
7. x²+4x+4/(x+2)(x-2) ​