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có 2 trường hợp
1. 1+2 = 5 + 10 = 15 ( Special )
2. 1+2=3 ( bình thường )
Trả lời
Vì 1 + 2 = 3
Mà 3 = 15
Suy ra 1 + 2 = 15
A. |-5| . (-7) + 4 . (-9)
= 5 . (-7) + 4 . (-9)
= (-35) + (-36)
= (-71)
B. 3 . (-5)2 + 2 . (-5) - 20
= 3 . 25 + 2 . (-5) - 20
= 75 + (-10) - 20
= 65 - 20
= 45
C. (15 - 10) - 15(34 - 10)
= 15 - 10 - (15 . 34 - 15 . 10)
= 15 . 1 - 10 - 15 . 34 + 15 . 10
= 15 . (1 - 34 + 10) - 10
= 15 . (-23) - 10
= (-345) - 10
= -355
D. 1 - 2 + 3 - 4 + 5 - 6 + .... + 2009 - 2010 + 2011
= (1 - 2) + (3 - 4) + .... + (2009 - 2010) + 2011
= (-1) + (-1) + .... + (-1) + 2011
2010 : 2 = 1005
= (-1) . 1005 + 2011
= (-1005) + 2011
= 1006
nếu 1 = 5
2 = 10
3 = 15
4 = 20
thì 5 = 1
hải yến ơi,k tớ nhé
a; - \(\dfrac{10}{13}\) + \(\dfrac{5}{17}\) - \(\dfrac{3}{13}\) + \(\dfrac{12}{17}\) - \(\dfrac{11}{20}\)
= - (\(\dfrac{10}{13}\) + \(\dfrac{3}{13}\)) + (\(\dfrac{5}{17}\) + \(\dfrac{12}{17}\)) - \(\dfrac{11}{20}\)
= - 1 + 1 - \(\dfrac{11}{20}\)
= 0 - \(\dfrac{11}{20}\)
= - \(\dfrac{11}{20}\)
b; \(\dfrac{3}{4}\) + \(\dfrac{-5}{6}\) - \(\dfrac{11}{-12}\)
= \(\dfrac{9}{12}\) - \(\dfrac{10}{12}\) + \(\dfrac{11}{12}\)
= \(\dfrac{10}{12}\)
= \(\dfrac{5}{6}\)
c; [13.\(\dfrac{4}{9}\) + 2.\(\dfrac{1}{9}\)] - 3.\(\dfrac{4}{9}\)
= [\(\dfrac{52}{9}\) + \(\dfrac{2}{9}\)] - \(\dfrac{4}{3}\)
= \(\dfrac{54}{9}\) - \(\dfrac{4}{3}\)
= \(\dfrac{14}{3}\)
a) \(\frac{15}{16}\cdot\frac{4}{3}-\frac{1}{2}:\frac{5}{4}+3\)
\(=\frac{5}{4}-\frac{2}{5}+3\)
\(=\frac{25}{20}-\frac{8}{20}+\frac{60}{20}\)
\(=\frac{77}{20}=3\frac{17}{20}\)
b) \(\left(\frac{2}{3}-\frac{3}{8}\right):\left(\frac{3}{5}+\frac{1}{4}\right)\)
\(=\frac{7}{24}:\frac{17}{20}\)
\(=\frac{35}{102}\)
c) \(\frac{15}{8}\cdot\left(\frac{1}{3}+\frac{1}{8}\right)-\frac{3}{8}:\frac{3}{4}\)
\(=\frac{15}{8}\cdot\frac{11}{24}-\frac{1}{2}\)
\(=\frac{55}{64}-\frac{1}{2}\)
\(=\frac{23}{64}\)
d) \(\frac{20}{21}:\left(\frac{4}{5}-\frac{1}{10}\right)+\frac{13}{15}:\frac{5}{26}\)
\(=\frac{20}{21}:\frac{7}{10}+\frac{52}{15}\)
\(=\frac{200}{147}+\frac{52}{15}\)
\(=4\frac{608}{735}\)
5 = 25
k mk nha
5 = 25
ko sai được
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