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Bài 1 :
A = 1 - 1/2 + 1/2 - 1/4 + 1/4 - 1/8 + 1/8 - 1/16 + ... + 1/32 - 1/64
A = 1 - 1/64
A = 63/64
12/5 -4/5 =8/5
11/6 -2/3 =21/18 =7/6
7/8 -2/7 =33/56
4 -8/5 =20/5-8/5 =12/5
2 -3/8 =16/8 -3/8 =13/8
16/7 -2 =16/7 -14/7 =2/7
25/4 -3=25/4 -12/4 =13/4
câu 2 : câu 3 :
a) 8/5 a)4 - 8/5 = 20/5 - 8/5 =12/5
b) 7/6 b)2 - 3/8 =16/8 - 3/8 = 13/8
c) 35/56 c)16/7 - 2 = 16/7 - 14/7 = 2/7
d)25/4 - 3 = 25/4 - 12/4 = 13/4
\(\frac{1}{2}:\frac{3}{2}:\frac{5}{4}:\frac{6}{5}:\frac{7}{6}:\frac{8}{7}\)
\(=\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{4}{5}\cdot\frac{5}{6}\cdot\frac{6}{7}\cdot\frac{7}{8}\)
\(=\frac{1\cdot\left(2\cdot5\cdot6\cdot7\right)}{8\cdot3\cdot\left(2\cdot5\cdot6\cdot7\right)}\)
\(=\frac{1}{24}\)
\(\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot\frac{4}{5}\cdot\frac{5}{6}\cdot\frac{6}{7}\cdot\frac{7}{8}\cdot\frac{8}{9}\cdot\frac{9}{10}\)
\(=\frac{1\cdot\left(2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot9\right)}{\left(2\cdot3\cdot4\cdot5\cdot6\cdot7\cdot8\cdot9\right)\cdot10}\)
\(=\frac{1}{10}\)
\(\left(2.8x-32\right):\frac{2}{3}=90\)
\(2.8\cdot x-32=90\cdot\frac{2}{3}\)
\(\frac{14}{5}x-32=60\)
\(\frac{14}{5}x=60+32\)
\(\frac{14}{5}x=92\)
\(x=\frac{230}{7}\)
B , c , d tương tự
\(1,\frac{3}{5}+\frac{7}{2}-\frac{4}{7}=\frac{42}{70}+\frac{245}{70}-\frac{40}{70}=\frac{247}{70}\)
\(2,\frac{4}{5}-\frac{1}{3}+\frac{3}{4}=\frac{48}{60}-\frac{20}{60}+\frac{45}{60}=\frac{73}{60}\)
\(3,\frac{1}{3}\times\frac{5}{7}:\frac{7}{2}=\frac{5}{21}:\frac{7}{2}=\frac{10}{147}\)
\(4,\frac{1}{2}:\frac{2}{7}\times\frac{4}{7}=\frac{7}{4}\times\frac{4}{7}=1\)
\(5,\frac{19}{15}\times\frac{3}{7}:\frac{4}{9}=\frac{19}{35}:\frac{4}{9}=\frac{171}{140}\)
\(6,\frac{11}{3}:\frac{9}{16}:\frac{3}{8}=\frac{176}{27}:\frac{3}{8}=\frac{1408}{81}\)
_Chúc bạn học tốt _
a) \(\frac{27}{36}=\frac{3}{4}\)
b) \(\frac{45}{60}=\frac{3}{4}\)
c) \(\frac{2}{4}=\frac{1}{2}\)
d) \(\frac{10}{12}=\frac{5}{6}\)
e) \(\frac{112}{252}=\frac{4}{9}\)
Đúng nha bạn !!@@
\(\frac{1}{3}+\frac{3}{4}x\frac{5}{9}=\frac{1}{3}+\frac{5}{12}=\frac{3}{4}\)
\(\frac{7}{12}-\frac{5}{4}x\frac{2}{15}=\frac{7}{12}-\frac{1}{6}=\frac{5}{12}\)
\(y+\frac{1}{4}=\frac{7}{8}-\frac{3}{8}=y+\frac{1}{4}=\frac{1}{2}=\frac{1}{2}-\frac{1}{4}=\frac{1}{4}\)
\(y-\frac{5}{12}=\frac{2}{3}-\frac{1}{4}=y-\frac{5}{12}=\frac{5}{12}=\frac{5}{12}+\frac{5}{12}=\frac{5}{6}\)
\(\frac{12}{7}xy=\frac{16}{21}=\frac{16}{21}:\frac{12}{7}=\frac{4}{9}\)
\(\frac{5}{4}:y=\frac{7}{12}=\frac{5}{4}:\frac{7}{12}=\frac{15}{7}\)