Tính hợp lý nhất :
a) 2155 – (174 + 2155) + (-68 + 174)
b) -25.72 + 25.21 – 49.25
c) 35 (14-23) – 23 (14 – 25)
d) 44.(-36) + 22.(-28)
Tính hợp lý nhất :
a) 2155 – (174 + 2155) + (-68 + 174)
b) -25.72 + 25.21 – 49.25
c) 35 (14-23) – 23 (14 – 25)
d) 44.(-36) + 22.(-28)
a) $2155-(174+2155)+(-68+174)$
$=2155-174-2155-68+174$
$=(2155-2155)+(-174+174)-68$
$=0+0-68$
$=-68$
b) $-25.72+25.21-49.25$
$=25.(-72+21-49)$
$=25.(-100)$
$=-2500$
c) $35.(14-23)-23.(14-25)$
$=35.14-35.23-23.14+23.25$
$=(35.14-23.14)+(-35.23+23.25)$
$=14.(35-23)+23.(-35+25)$
$=14.12+23.(-10)$
$=168+(-230)$
$=-62$
d) $44.(-36)+22.(-28)$
$=22.2.(-36)+22.(-28)$
$=22.(-72)+22.(-28)$
$=22.(-72-28)$
$=22.(-100)$
$=-2200$