当a=-2时,a+2a+3a+4a+.+100a=
问题描述:
当a=-2时,a+2a+3a+4a+.+100a=
答
=[(100+1)×100÷2]a
=5050a
=-10100
当a=-2时,a+2a+3a+4a+.+100a=
=[(100+1)×100÷2]a
=5050a
=-10100