tinh
1-(2:3)-(2:9)-(2:27)-(2:81)-(2:243)
(goi y đổi thành phân số để tính)
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\(1-\frac{2}{3}-\frac{2}{9}-\frac{2}{27}-\frac{2}{81}-\frac{2}{243}\)
\(=\frac{243}{243}-\frac{162}{243}-\frac{54}{243}-\frac{6}{243}-\frac{2}{243}=\frac{1}{243}\)
e quy đồng ra nháp rồi cộng các số phù hợp là ra kết quả
(\(\dfrac{2}{3}\) + \(\dfrac{8}{9}\) + \(\dfrac{26}{27}\) + \(\dfrac{80}{81}\) + \(\dfrac{242}{243}\)) : y = 5
Đăt A = \(\dfrac{2}{3}\) + \(\dfrac{8}{9}\) + \(\dfrac{26}{27}\) + \(\dfrac{80}{81}\) + \(\dfrac{242}{243}\)
3A = 2 + \(\dfrac{8}{3}\) + \(\dfrac{26}{9}\) + \(\dfrac{80}{27}\) + \(\dfrac{242}{81}\)
3A - A = 2 + \(\dfrac{8}{3}\) + \(\dfrac{26}{9}\) + \(\dfrac{80}{27}\) + \(\dfrac{242}{81}\) - \(\dfrac{2}{3}\)-\(\dfrac{8}{9}\)-\(\dfrac{26}{27}\)-\(\dfrac{80}{81}\)-\(\dfrac{242}{243}\)
A x (3 - 1) = 2 - \(\dfrac{242}{243}\)+ (\(\dfrac{8}{3}\) - \(\dfrac{2}{3}\))+(\(\dfrac{26}{9}\) - \(\dfrac{8}{9}\))+(\(\dfrac{80}{27}\)-\(\dfrac{26}{27}\))+(\(\dfrac{242}{81}\)-\(\dfrac{80}{81}\))-\(\dfrac{242}{243}\)
A x 2 = 2 - \(\dfrac{242}{243}\) + 2 + 2 + 2 + 2
A x 2 = (2 + 2 + 2 +2 + 2) - \(\dfrac{242}{243}\)
A x 2 = 2x5 - \(\dfrac{242}{243}\)
A x 2 = 10 - \(\dfrac{242}{243}\)
A x 2 = \(\dfrac{2188}{243}\)
A = \(\dfrac{2188}{243}\) : 2
A = \(\dfrac{1094}{243}\)
\(\dfrac{1094}{243}\) : y = 5
y = \(\dfrac{1094}{243}\) : 5
y = \(\dfrac{1094}{1215}\)
\(x\) \(\times\) \(\dfrac{1}{4}\) = 6 : 1 : 2
\(x\) \(\times\) \(\dfrac{1}{4}\) = 6:2
\(x\) \(\times\) \(\dfrac{1}{4}\) = 3
\(x\) = 3 : \(\dfrac{1}{4}\)
\(x\) = 12
Ta có :C= 2181-729+243.81-27
=2052+19683-27
C=21108
D=\(3^2.9^2.243+18.243.324.243\)
=9.81.243+18.243.324.243
=177147+344373768
=344550915
Ta có : C:D=21108:344550915=0,00006
1- 2/3 -2/9-2/27-2/81-2/243
rồi tự tính hại não v;l