ai giải giúp bài này vs
1/3 +1/3^2+1/3^3+1/3^4+1/3^5+1/3^6
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\(\dfrac{3}{8}\times\dfrac{2}{3}+\dfrac{1}{4}=\dfrac{6}{24}+\dfrac{1}{4}=\dfrac{6}{24}+\dfrac{6}{24}=\dfrac{12}{24}=\dfrac{1}{2}\)
\(\dfrac{1}{3}:\dfrac{2}{9}-\dfrac{5}{6}=\dfrac{1}{3}\times\dfrac{9}{2}-\dfrac{5}{6}=\dfrac{9}{6}-\dfrac{5}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)
#YTVA
a ) 13/20
B)
C..........................................................
minh dang tính
\(-\frac{1}{7}+\frac{5}{3}+\frac{5}{4}+\frac{1}{3}-\frac{3}{2}\)
\(=\left(-\frac{1}{7}+\frac{5}{3}-\frac{3}{2}\right)+\left(\frac{5}{3}+\frac{1}{3}\right)\)
\(=\frac{-6}{42}+\frac{70}{42}-\frac{63}{42}+\frac{6}{3}\)
\(=\frac{-6+70-63}{42}+2\)
\(=\frac{1}{42}+\frac{84}{42}\)
\(=\frac{85}{42}\)
c)\(\dfrac{3}{8}\times\dfrac{5}{8}+y=\dfrac{5}{4}\)
\(\dfrac{15}{64}+y=\dfrac{5}{4}\)
\(y=\dfrac{5}{4}-\dfrac{15}{64}\)
\(y=\dfrac{65}{64}\)
d, \(\dfrac{3}{8}+\dfrac{5}{8}\times y=\dfrac{5}{4}\)
\(\dfrac{5}{8}\times y=\dfrac{5}{4}-\dfrac{3}{8}\)
\(\dfrac{5}{8}\times y=\dfrac{7}{8}\)
\(y=\dfrac{7}{8}:\dfrac{5}{8}\)
\(y=\dfrac{7}{5}\)
a, 3/4 x y = 3/5 + 3/10
3/4 x y = 9/10
y = 9/10 : 3/4
y = 6/5
b, 3/5 : y = 3/4 - 2/5
3/5 : y = 7/20
y = 3/5 : 7/20
y = 12/7
Vd1:
d) Ta có: \(\sqrt{2}\left(x-1\right)-\sqrt{50}=0\)
\(\Leftrightarrow\sqrt{2}\left(x-1-5\right)=0\)
\(\Leftrightarrow x=6\)
\(\frac{4}{3}-\left(x-\frac{1}{5}\right)=\left|\frac{-3}{10}+\frac{1}{2}\right|-\frac{1}{6}\)
\(\frac{4}{3}-\left(x-\frac{1}{5}\right)=\frac{1}{5}-\frac{1}{6}\)
\(\frac{4}{3}-\left(x-\frac{1}{5}\right)=\frac{1}{30}\)
\(x-\frac{1}{5}=\frac{4}{3}-\frac{1}{30}\)
\(x-\frac{1}{5}=\frac{13}{10}\)
\(x=\frac{13}{10}+\frac{1}{5}\)
\(x=\frac{3}{2}\)
Đặt \(A=\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+...+\frac{1}{3^6}\)
\(\Rightarrow3A=1+\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^5}\)
\(\Rightarrow3A-A=\left(1+\frac{1}{3}+...+\frac{1}{3^5}\right)-\left(\frac{1}{3}+\frac{1}{3^2}+...+\frac{1}{3^6}\right)\)
\(\Rightarrow2A=1-\frac{1}{3^6}\)
\(\Rightarrow A=\frac{1-\frac{1}{3^6}}{2}\)
Chúc bạn học tốt !!!!