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a, 6257+989+743
=(6257+743)+989
=7000+989
=7989
b, 5798+322+4678
=(4678+322)+5798
=5000+5798
=10798
a,6257+989+743=(6257+743)+989=7000+989=7989
b,5798+322+4678=5798+(322+4678)=5798+5000=10798
a) 6257 + 989 + 743
= 6257 +743 + 989
= 7000 + 989 = 7989
b) 5798 + 322 + 4678
= 5798 + 5000 = 10798
5798 + 322 + 4678
= 5798 + ( 322 + 4678 )
= 5798 + 5000
= 10798
k mk nha
9+3+2+1+7+8+5+10+6+4= (9+1)+(2+8)+(3+7)+(4+6)+5=10+10+10+10+5=10.4+5=40+5=45
\(\left(1-\frac{1}{12}\right).\left(1-\frac{1}{11}\right).\left(1-\frac{1}{10}\right).\left(1-\frac{1}{9}\right).\left(1-\frac{1}{8}\right)\)
\(=\left(\frac{12}{12}-\frac{1}{12}\right).\left(\frac{11}{11}-\frac{1}{11}\right).\left(\frac{10}{10}-\frac{1}{10}\right).\left(\frac{9}{9}-\frac{1}{9}\right).\left(\frac{8}{8}-\frac{1}{8}\right)\)
\(=\frac{11}{12}.\frac{10}{11}.\frac{9}{10}.\frac{8}{9}.\frac{7}{8}\)
\(=\frac{11.10.9.8.7}{12.11.10.8.9}\)
\(=\frac{7}{12}\)
Chúc bạn học tốt !!!
\(\left(1-\frac{1}{12}\right)\left(1-\frac{1}{11}\right)\left(1-\frac{1}{10}\right)\left(1-\frac{1}{9}\right)\left(1-\frac{1}{8}\right)\)
\(=\frac{11}{12}.\frac{10}{11}.\frac{9}{10}.\frac{8}{9}.\frac{7}{8}\)
\(=\frac{11.10.9.8.7}{12.11.10.9.8}\)
\(=\frac{7}{12}\)
\(\frac{2}{3}\times\frac{4}{5}+\frac{4}{5}\times\frac{1}{2}+\frac{4}{5}\times\frac{1}{6}\)
\(=\left(\frac{2}{3}+\frac{1}{2}+\frac{1}{6}\right)\times\frac{4}{5}\)
\(=\frac{4}{3}\times\frac{4}{5}\)
\(=\frac{16}{15}\)
a,Ta có \(\frac{x}{6}=\frac{2}{3}\)
\(\Rightarrow3x=12\Rightarrow x=4\)
Vậy x = 4
b, \(\left(\frac{4}{7}+\frac{8}{9}\right)-\frac{5}{9}=\frac{4}{7}+\frac{8}{9}-\frac{5}{9}\)
\(=\frac{4}{7}+\left(\frac{8}{9}-\frac{5}{9}\right)\)
\(=\frac{4}{7}+\frac{1}{3}\)
\(=\frac{19}{21}\)
Bài 1 mình nhầm. x phần 6 = 4 phần 7 mới đúng. Cảm ơn bạn nhé