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Bài 1:
a: =25+75=100
b: =60-17-43+12=12
c: =-2-18=-20
d: =-3+36-17=36-20=16
Bài 2:
a: =-102
b: =-1000
c: =12x15=180
d: =21x(-10)=-210
A = - \(\dfrac{1}{21}\) - \(\dfrac{1}{28}\)
A =- \(\dfrac{4}{84}\)- \(\dfrac{3}{84}\)
A = -\(\dfrac{7}{84}\)
A = - \(\dfrac{1}{12}\)
B = - \(\dfrac{8}{18}\) - \(\dfrac{15}{27}\)
B = - \(\dfrac{4}{9}\) - \(\dfrac{5}{9}\)
B = -1
C = - \(\dfrac{5}{12}\) + 0,75
C = -\(\dfrac{5}{12}\) + \(\dfrac{3}{4}\)
C = - \(\dfrac{5}{12}\) + \(\dfrac{9}{12}\)
C = \(\dfrac{4}{12}\)
C= \(\dfrac{1}{3}\)
D = 3,5 - { - \(\dfrac{2}{7}\))
D = \(\dfrac{7}{2}\) + \(\dfrac{2}{7}\)
D = \(\dfrac{49}{14}\) + \(\dfrac{4}{14}\)
D = \(\dfrac{53}{14}\)
Bài 1:
a; \(\dfrac{5}{18}\) + \(\dfrac{8}{19}\) - \(\dfrac{7}{21}\) + (- \(\dfrac{10}{36}\) + \(\dfrac{11}{19}\) + \(\dfrac{1}{3}\)) - \(\dfrac{5}{8}\)
= \(\dfrac{5}{18}\) + \(\dfrac{8}{19}\) - \(\dfrac{1}{3}\) -\(\dfrac{10}{36}\) + \(\dfrac{11}{19}\) + \(\dfrac{1}{3}\) - \(\dfrac{5}{8}\)
= (\(\dfrac{5}{18}\) - \(\dfrac{10}{36}\)) + (\(\dfrac{8}{19}\) + \(\dfrac{11}{19}\)) - (\(\dfrac{1}{3}\) - \(\dfrac{1}{3}\)) - \(\dfrac{5}{8}\)
= (\(\dfrac{5}{18}\) - \(\dfrac{5}{18}\)) + \(\dfrac{19}{19}\) - 0 - \(\dfrac{5}{8}\)
= 0 + 1 - \(\dfrac{5}{8}\)
= \(\dfrac{3}{8}\)
b; \(\dfrac{1}{13}\) + (\(\dfrac{-5}{18}\) - \(\dfrac{1}{13}\) + \(\dfrac{12}{17}\)) - (\(\dfrac{12}{17}\) - \(\dfrac{5}{18}\) + \(\dfrac{7}{5}\))
= \(\dfrac{1}{13}\) - \(\dfrac{5}{18}\) - \(\dfrac{1}{13}\) + \(\dfrac{12}{17}\) - \(\dfrac{12}{17}\) + \(\dfrac{5}{18}\) - \(\dfrac{7}{5}\)
= (\(\dfrac{1}{13}\) - \(\dfrac{1}{13}\)) + (\(\dfrac{12}{17}\) - \(\dfrac{12}{17}\)) + (-\(\dfrac{5}{18}\) + \(\dfrac{5}{18}\)) - \(\dfrac{7}{5}\)
= 0 + 0 + 0 - \(\dfrac{7}{5}\)
= - \(\dfrac{7}{5}\)
Bài 1 c;
\(\dfrac{15}{14}\) - (\(\dfrac{17}{23}\) - \(\dfrac{80}{87}\) + \(\dfrac{5}{4}\)) + (\(\dfrac{17}{23}\) - \(\dfrac{15}{14}\) + \(\dfrac{1}{4}\))
= \(\dfrac{15}{14}\) - \(\dfrac{17}{23}\) + \(\dfrac{80}{87}\) - \(\dfrac{5}{4}\) + \(\dfrac{17}{23}\) - \(\dfrac{15}{14}\) + \(\dfrac{1}{4}\)
= (\(\dfrac{15}{14}-\dfrac{15}{14}\)) + (\(-\dfrac{17}{23}+\dfrac{17}{23}\)) - (\(\dfrac{5}{4}\) - \(\dfrac{1}{4}\)) + \(\dfrac{80}{87}\)
= 0 + 0 - 1 + \(\dfrac{80}{87}\)
= - \(\dfrac{7}{87}\)
Bài 1 :
a, 25 + (-42) = - ( 42 - 25 ) = - 17
b, (-17) + 5 + 8 + 17 + (-3 )
= [ (-17) + 17 ] + [ ( 5 + 8 ) + (-3) ]
= 0 + 10
= 10
c, 25. 22 - ( 15-18 ) + ( 12 - 19 + 10 )
= 25 . 4 - (-3) + 3
= 100 - [ (-3) + 3 ]
= 100 - 0
= 100
d, 120 - 35 + 29 - 242
= 85 + 29 - 242
= 114 - 242
= -128
a) | -18 | + ( -12 )
= 18 - 12
= 6
b) ( -20 ) + | -88 |
= -20 + 88
= 68
c) | -37 | + ( - | 15 | )
= 37 - 15
= 22
d) 99 - [ 109 + ( -9 ) ]
= 99 - 100
= -1
Chọn B