计算:
(1)(-x)·x2(-x)6;
(2)(-2x2)3+x2·x4-(-3x3)2.
观察下列等式:
39×41=402-12,48×52=502-22,56×64=602-42,65×75=702-52,83×97=902-72,…请你把发现的规律用字母表示出来:m×n=________.
已知am=2,an=5,则a3m+n=________.
若代数式x2+(2a-6)xy+y2+9中不含xy项,则a=________.
计算:2019×(-4)1010=________.
若a2+ab=15,b2+ab=6,则a2-b2=__________.