Question

1+(-2)+3+(-4)+...+39+(-40)

Answer 1

Ta có : 1 + (-2) + 3 + (-4)+ .........+ 39 + (-40)

= [ 1+(-2)] + [3+(-4)]+..........+ [39+(-40] ( 20 nhóm )

= (-1) + (-1)+..........................+(-1) ( 20 số)

= (-1) . 20

= - 40

Answer 2

1+(-2)+3+(-4)+...+39+(-40)

=\(\left[1+\left(-2\right)\right]+\left[3+\left(-4\right)\right]+......+\left[39\left(-40\right)\right]\)

=\(\left(-1\right)+\left(-1\right)+\left(-1\right)+........\)

= -20

Answer 3

1+(-2)+3+(-4)+...+39+(-40)

= (1-40).[(-40-1):2+1]=-780

đúng V hộ cái

Answer 4

1+(-2)+3+(-4)+...+39+(-40)

= [1+(-2)]+[3+(-4)]+...+[39+(-40)]

= (-1)+(-1)+...+(-1)

= (-1).20= -20