Tính một cách hợp lí:
a) (- 17) + (- 23) + 44;
b) (- 39) + (- 16) + 39.
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a) 15.(-236) + 15.235
= 15.(-236 + 235)
= 15.(-1)
= -15
b) 237.(-28) + 28.137
= 237.(-28) - (-28).137
= (-28).(237 - 137)
= (-28).100
= -2800
c) 38.(27 - 44) - 27.(38 - 44)
= 38.27 - 38.44 - 27.38 + 27.44
= (38.27 - 27.38) + (-38). 44 + 27 . 44
= 0 + 44.[(-38)+27]
= 44.(-11)
= -484
a) 21 - 22 + 23 - 24
= (21 - 22) + (23 - 24)
= (-1) + (-1) = -2
b) 125 - (115 - 99)
= 125 - 115 + 99
= (125 - 115) + 99
= 10 + 99 = 109.
a) Ta có: \(17\cdot\left[29-\left(-111\right)\right]+29\cdot\left(-17\right)\)
\(=17\cdot\left[29+111-29\right]\)
\(=17\cdot111=1887\)
b) Ta có: \(19\cdot43+\left(-20\right)\cdot43-\left(-40\right)\)
\(=43\cdot\left(19-20\right)+40\)
\(=-43+40=-3\)
\(a.21-22+23-24\)
\(=\left(-1\right)+\left(-1\right)=-2\)
\(b.125-\left(115-99\right)\)
\(=125-16=109\)
a) 4.(1 930 + 2 019) + 4.(-2 019)
= 4.(1 930 + 2 019 - 2 019)
= 4.1 930
= 7 720
b) (-3).(-17) + 3.(120 - 17)
= 3.17 + 3.(120 - 17)
= 3.(17 + 120 - 17)
= 3.120
= 360
a) 12 + 13 + 14 - 15 - 16 - 17
= (12 - 15) + (13 - 16) + (14 - 17)
= (-3) + (-3) + (-3) = -9
b) (35 - 17) - (25 - 7 + 22)
= 35 - 17 - 25 + 7 - 22
= (35 - 25) - (17 - 7) - 22
= 10 - 10 - 22 = -22
\(a.\)
\(\dfrac{27}{13}-\dfrac{106}{111}+-\dfrac{5}{111}=\dfrac{27}{13}-\dfrac{106}{111}-\dfrac{5}{111}=\dfrac{27}{13}-\left(\dfrac{106+6}{111}\right)=\dfrac{27}{13}-1=\dfrac{14}{13}\)
\(b.\)
\(\dfrac{12}{11}-\dfrac{-7}{19}+\dfrac{12}{19}=\dfrac{12}{11}+\dfrac{7}{19}+\dfrac{12}{19}=\dfrac{12}{11}+1=\dfrac{23}{11}\)
\(c.\)
\(\dfrac{5}{17}-\dfrac{25}{31}+\dfrac{12}{17}+-\dfrac{6}{31}=\left(\dfrac{5}{17}+\dfrac{12}{17}\right)-\left(\dfrac{25}{31}+\dfrac{6}{31}\right)=1-1=0\)
a) \(\dfrac{27}{13}-\dfrac{106}{111}+\dfrac{-5}{111}=\dfrac{27}{13}+\left(\dfrac{-106}{111}+\dfrac{-5}{111}\right)=\dfrac{27}{13}+-1=\dfrac{14}{13}\)
b) \(\dfrac{12}{11}-\dfrac{-7}{19}+\dfrac{12}{19}=\dfrac{12}{11}+\left(\dfrac{7}{19}+\dfrac{12}{19}\right)=\dfrac{12}{11}+1=\dfrac{23}{11}\)
c)\(\dfrac{5}{17}-\dfrac{25}{31}+\dfrac{12}{17}+\dfrac{-6}{31}=\left(\dfrac{5}{17}+\dfrac{12}{17}\right)+\left(\dfrac{-25}{31}+\dfrac{-6}{31}\right)=1+-1=0\)
a,(-15)-23+(-85)-77=[(-15)+(-85)]-(23+77)=(-100)-100=-200
b,(-24) + 4 + (-6) + 26 =[(-24)+(-6)]+(4+26)=(-30)+30=0
c, 34 + 35 + 36 + 37 - 14 - 15 - 16 - 17 =(34-14)+(35-15)+(36-16)+(37-17)=20+20+20+20=80
\(a)\left(-17\right)+\left(-23\right)+44=-40+44=4\)
\(b)\left(-39\right)+\left(-16\right)+39=\left[\left(-39\right)+39\right]+\left(-16\right)=0+\left(-16\right)=-16\)
a) (- 17) + (- 23) + 44;
= (- 40) + 44
= 4
b) (- 39) + (- 16) + 39.
= (- 39) + 39 + (- 16)
= 0 + (- 16)
= - 16