Question

tính hợp lí;

a,(-2)+7+(-12)+17+...+(-52)+57

b,(-30)+(-29)+...+48+49+50

Answer 1

a,(-2)+7+(-12)+17+...+(-52)+57

=[(-2)+7]+[(-12)+17]+...+[(-52)+57]

=5+5+5+...+5               có 6 số 5

=5.6

=30

b,(-30)+(-29)+...+48+49+50

=[(-30)+(-29)]+...+31+32+...+50

=0+0+...+31+32+...+50

=0+31+32+...+50

=810

Answer 2

a, (-2+7)+(-12+17)+...+(-52+57)

=5+5+...+5

=5.6=30

Answer 3

b,(-30)+(-29)+...48+49+50

=(-30+30)+(-29+29)+...+(-1+1)+0+31+32+...+50

=0+0+0+...+0+31+32+...+50

=20.(31+50)=20.81=1620