1.(m-3n)平方-(m+3n)平方=m^2-6mn+9n^2-m^2-6mn-9n^2=-12mn
2.(a+b-c)(a+b+c)=(a+b)^2-c^2=a^2+2ab+b^2-c^2
3.3a平方-a(3a-5b)-b(2a-b)=3a^2-3a^2+5ab-2ab+b^2=3ab+b^2
4.(3x+2)(x-1)-3(x+3)(x-3)=3x^2-x-2-3x^2+27=-x+25
5.(2a-b)平方-(2a+b)(2a-b)=4a^2-4ab+b^2-4a^2+b^2=-4ab+2b^2