1题（m-n-3）² = 2题（a²+9)²-(a+3)(a-3)(a²+9)=

原式=m²+n²+9+2mn+6m-6n
原式=（a²+9）²-(a²-9)(a²+9)
              =(a²+9)(a²+9-a²+9)
              =18(a²+9)
              =18a²+162
 3.   原式=（a-2)(a²-4a+4+6a)+ (a+3)(a²+6a+9-9a)
              =  (a-2)(a²+2a+4)+(a+3)(a²-3a+9)
              =a(a-2)(a+2)+4(a-2)+a(a+3)(a-3)+9(a+3)
              =a(a²-4)+4a-8+a(a²-9)+9a+27
              =a*3-4a+4a-8+a*3-9a+9a+27
              =2a*3+19
4.   原式=(x+y-2x+2y)²
             =(3y-x)²
             =9y²-6xy+x²
5.   符号打错了吧,没法儿解.