用简便方法计算
(1)2019×2021
(2)1032
(3)5(6+1)(62+1)(64+1)(68+1)(616+1)+1
若5x-3y-6=0,则105x÷103y=________
已知,则(x-1)(3x+1)-(x+1)2-3的值为________.
计算:-48 x3y2÷6x2y=__________
计算:(a+2b)2=_________________.
计算:__________.