Đáp án:
g) 31.(-18)+31.(-81)-31
= 31.(-18)+31.(-81)+(-31)
= 31.(-18)+31.(-81)+31.(-1)
= 31.[(-18)+(-81)+(-1)]
= 31.(-100)
= -3100
h) (-12).47+(-12).52+(-12)
= (-12).47+(-12).52+(-12).1
= (-12).(47+52+1)
= (-12).100
= -1200
k) 13.(23+22)-3.(17+28)
= 13.45-3.45
= 45.(13-3)
= 45.10
= 450
m) (-48)+48.(-78)+48.(-21)
= 48.(-1)+48.(-78)+48.(-21)
= 48.[(-1).(-78)+(-21)]
= 48.(-100)
= -4800
n) 135.(171-123)-171.(135-123)
= 135.48-171.12
= 6480-2052
= 4428
p) -(-2009+97)-74.(-18)+74.(-118)-2009-3
= -(-1912)-74.(-18)+74.(-118)-2009-3
= 1912 -74.(-18)+74.(-118)-2009-3
= 1912+(-74).(-18)+74.(-118)-2009-3
= 1912+74.(-1).(-18)+74.(-118)-2009-3
= 1912+74.18+74.(-118)-2009-3
= 1912 +74.[18+(-118)]-2009-3
= 1912 +74.(-100)-2009-3
= 1912 +(-7400)-2009-3
= 1912 -2009-3+(-7400)
= (-97)-3+(-7400)
= (-100)+(-7400)
= -7500
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