Question

Tính hhợplis ( nếu có )

a) 23-42

b) 21 + (-67) + (-21) + 120 + 67

c) (-34 + 137) - (137-34+60)

Answer 1

\(a,23-42=-19\\ b,21+\left(-67\right)+\left(-21\right)+120+67\\ =\left[21+\left(-21\right)\right]+\left[\left(-67\right)+67\right]+120\\ =0+0+120\\ =120\\ c,\left(-34+137\right)-\left(137-34+60\right)\\ =-34+137-137+34-60\\ =\left(-34+34\right)+\left(137-137\right)-60\\ =0+0-60\\ =-60\)

Answer 2

\(a,23-42=-19\\ b,21+\left(-67\right)+\left(-21\right)+120+67=21+\left(-21\right)+\left(-67\right)+67+120=0+0+120=120\\ c,\left(-34+137\right)-\left(137-34+60\right)=-34+137-137+34-60=\left(-34+34\right)+\left(137-137\right)-60=0+0-60=-60\)

Answer 3

a) 23 - 42 = 42 - 23 = 19

b) 21 + (–67) + (-21) +120 + 67 = [21+ (-21)] + [(-67) + 67] + 120 = 120

c) (-34 + 137) - (137 - 34 + 60) = -34 + 137 - 137 + 34 - 60 = (-34 + 34) + 137 - 137 - 60 = -60