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a)=1/2 . 8/15 - 3/4.47/9
=4/15 - 47/12
=-73/20
b)=2-1/3 . -21/20
=2+7/20
=47/20
\(\frac{1}{2}+\frac{1}{2}.\frac{1}{3}+\frac{1}{3}.\frac{1}{4}+\frac{1}{4}.\frac{1}{5}+...+\frac{1}{9}.\frac{1}{10}\)
\(=\frac{1}{2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{9.10}\)
\(=\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{9}-\frac{1}{10}\)
\(=\frac{1}{2}+\frac{1}{2}-\frac{1}{10}\)
\(=\frac{9}{10}\)
a) Ta có : ( x+3 ).( x- 5 ) = 0
suy ra: x+3 = 0 hoặc x - 5 = 0
suy ra : x = -3 hoặc x = 5
KL : Vậy x = -3 hoặc x = 5
a. \(\frac{1}{5}+\frac{3}{4}+\frac{1}{10}\)
= \(\frac{4}{20}+\frac{15}{20}+\frac{2}{20}\)
= \(\frac{21}{20}\)
b. \(\frac{5}{6}-\frac{1}{3}+\frac{1}{6}\)
= \(\frac{5}{6}-\frac{2}{6}+\frac{1}{6}\)
= \(\frac{4}{6}=\frac{2}{3}\)
c. \(\frac{3}{8}-\frac{10}{2}:\frac{4}{5}\)
= \(\frac{3}{8}-\frac{50}{8}\)
= \(\frac{-47}{8}\)
a) \(\frac{1}{5}+\frac{3}{4}+\frac{1}{10}\)
= \(\frac{4+15+2}{20}\)
= \(\frac{21}{20}\)
b) \(\frac{5}{6}-\frac{1}{3}+\frac{1}{6}\)
= \(\frac{5-2+1}{6}\)
= \(\frac{4}{6}\)
c) \(\frac{3}{8}-\frac{10}{2}:\frac{4}{5}\)
= \(\frac{3}{8}-\frac{25}{4}\)
= \(-\frac{47}{8}\)
1, Ta có :
\(x+\frac{3}{5}=\frac{4}{7}\div\frac{8}{21}\)
\(x+\frac{3}{5}=\frac{4}{7}\times\frac{21}{8}\)
\(x+\frac{3}{5}=\frac{3}{2}\)
\(x=\frac{3}{2}-\frac{3}{5}\)
\(x=\frac{15}{10}-\frac{6}{10}\)
\(x=\frac{9}{10}\)
Vậy x = \(\frac{9}{10}\)
2, Ta có :
\(\frac{2}{3}+\frac{3}{4}\div x=-\frac{1}{6}\)
\(\frac{3}{4}\div x=-\frac{1}{6}-\frac{2}{3}\)
\(\frac{3}{4}\div x=-\frac{1}{6}-\frac{4}{6}\)
\(\frac{3}{4}\div x=-\frac{5}{6}\)
\(x=\frac{3}{4}\div\left(-\frac{5}{6}\right)\)
\(x=\frac{3}{4}\times\left(-\frac{6}{5}\right)\)
\(x=-\frac{9}{10}\)
Vậy x = \(-\frac{9}{10}\)
thanks bạn nha