若实数m,n满足(m-1)2+=0,则(m+n)5= .
代数式的意义为___________.
计算: (1)199.92=_______;(2)512=________;(3)1-2×51+512=_______.
计算:-3a×(-3a)=________.
计算:-3a+(-3a)=________;
计算:(m-n)(m+n)=________;