代数式的值是-2,则的值是 .
a2bx3÷a2x=_________;
填空: (1)1010÷______=109;(2)a8÷a4=_____;(3)(-b)9÷(-b)7=________; (4)x7÷_______=1;(5)(y5)4÷y10=_______;(6)(-xy)10÷(-xy)5=_________.
若3n=27,则21-n=______.
当x______时,(3x+2)0=1有意义,若代数式(2x+1)-4无意义,则x=________.
(1)当x_______时,=-2有意义; (2)当x_______时,(x+5)0=1有意义; (3)当x_______时,(x+5)-2=1有意义.