a.-20
b.13
c.-30
d.0
nhớ
a, [-30] + 15 + 10 + [-15]
= [-30 + 10]+ [15 + [-15]]
= -20 + 0
= -20
b, 17 + [-12] + 25 - 17
= [17 - 17] + [-12 + 25]
= 0 + 13
= 13
c, [-14] + 250 + [-16] + [- 250]
= [-14 + [ -16]] + [ 250 + [ -250]]
= -20 + 0
= -20
d, [-3] + [-14] + 27 + [ -10]
= - [ 3 + 14] +27 - 10
= [ - 27 + 27] - 10
= 0 - 10
= - 10
5. Tính tổng:
a) (-30) + 15 + 10 + ( -15)
= (-30 + 10) + [15 + (-15)]
= -20 + 0
= -20
b) 17 + ( -12) + 25 – 17
= (17 - 17) + (-12+25)
= 0 + 13
= 13
c) ( -14 ) + 250 + ( - 16) + (- 250)
= [-14 + (-16)] + [250 + (-250)]
=-30+0
=-30
d) ( -3) + ( - 14) + 27 + ( -10)
= [-3 + (-14)] + 27 - 10
= -27 + 27 - 10
= (-27+27)-10
=0-10
=-10