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a) (65+27-49) - ( 45+37-19)
= 65+27-49 - 45 -37+19
= (65-45)+ ( 27-37) + (-49+19)
= 20 + (-10) + (-30)
= -20
A=[12-(-3)]-[3-(-20)+(-3)]
=>A=12+3-(3+20-3)
=>A=12+3-3-20+3
=>A=15-3-20+3
=>A=12-20+3
=>A=-8+3
=>A=-5
a) \(2021^{2020}-2021^{2019}=2021^{2019}.\left(2021-1\right)=2021^{2019}.2020\)
b) Ta có :\(7x-140=3.7^2\)
\(\implies\) \(7x-140=3.49\)
\(\implies\) \(7x-140=147\)
\(\implies\) \(7x=287\)
\(\implies\) \(x=41\)
A =\(\frac{7}{19}.\frac{8}{11}+\frac{7}{19}.\frac{3}{11}+\frac{12}{19}\)
A = \(\frac{7}{19}.\left(\frac{8}{11}+\frac{3}{11}\right)\)+ \(\frac{12}{19}\)
A = \(\frac{7}{19}.1+\frac{12}{19}\)
A = \(\frac{7}{19}+\frac{12}{19}\)
A = 1
--------
B = \(\frac{5}{9}.\frac{7}{13}+\frac{5}{9}.\frac{9}{13}-\frac{5}{9}.\frac{3}{13}\)
B = \(\frac{5}{9}.\left(\frac{7}{13}+\frac{9}{13}-\frac{3}{13}\right)\)
B = \(\frac{5}{9}.1\)
B = \(\frac{5}{9}\)
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C = \(\left(\frac{67}{111}+\frac{2}{33}-\frac{15}{117}\right).\left(\frac{1}{3}-\frac{1}{4}-\frac{1}{12}\right)\)
C = \(\left(\frac{67}{111}+\frac{2}{33}-\frac{15}{117}\right).\left(\frac{4}{12}-\frac{3}{12}-\frac{1}{12}\right)\)
C = \(\left(\frac{67}{111}+\frac{2}{33}-\frac{15}{117}\right).0\)
C = 0
Chúc bạn học tốt
A=-11 X=
a=11 nhabanj