1.=a*a+b*b-(a*a-b*b)=2ab+2b*b
2.=6xy+4y*y(套上面的公式)
3.=(a*a-b*b)-( b*b-a*a)=2a*a-2b*b
4.=2*3a*3a-2*2a*2a=18a*a-18b*b
5.=[a+(b+c)][a+(b+c)]-[a-(b+c)][a-(b+c)]=2a(b+c)+2(b+c)(b+c)
=2...
1.=a*a+b*b-(a*a-b*b)=2ab+2b*b
2.=6xy+4y*y(套上面的公式)
3.=(a*a-b*b)-( b*b-a*a)=2a*a-2b*b
4.=2*3a*3a-2*2a*2a=18a*a-18b*b
5.=[a+(b+c)][a+(b+c)]-[a-(b+c)][a-(b+c)]=2a(b+c)+2(b+c)(b+c)
=2...