Question

(-1)+2+(-3)+4+…(-99)+100;等于?

Answer 1

(-1)+2+(-3)+4+…(-99)+100

=（-1+2）+（-3+4）+……+（-99+100）

= -1×50

= -50

3+(-6)+6+(-9)+…27+(-30)

=3-6+6-9+……+27-30

=3-30

= -27