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đùa à bất kì số thập phân hữu hạn nào luỹ thừa lên cũng = 0 nên nó rất dễ giải:
a) \(\left[0,\left(3\right)\right]^2-\dfrac{81}{82}+2\)
= \(0-\dfrac{81}{82}+2\)
= \(\left(0+2\right)-\dfrac{81}{82}\)
= \(2-\dfrac{81}{82}\)
= \(\dfrac{83}{82}\)
b) \(3-\dfrac{1}{49}+\left[0,\left(142857\right)\right]^2\)
= \(3-\dfrac{1}{49}+0\)
= \(\left(3+0\right)-\dfrac{1}{49}\)
= \(3-\dfrac{1}{49}\)
= \(\dfrac{146}{49}\)
mình rút gọn luôn đó nhe 
a)
\(\left[0,\left(3\right)\right]^2-\dfrac{81}{82}+2\\ =\dfrac{1}{9}-\dfrac{81}{82}+2\\ =\dfrac{82}{738}-\dfrac{729}{738}+\dfrac{1479}{738}\\ =\dfrac{82-729+1479}{738}\\ =\dfrac{832}{738}\\ \approx1,13\)
b)
\(3-\dfrac{1}{49}+\dfrac{1}{7}\\ =\dfrac{147}{49}-\dfrac{1}{49}+\dfrac{7}{49}\\ =\dfrac{147-1+7}{49}\\ =\dfrac{153}{49}\\ \approx3,12\)
a)
\(\begin{array}{l}\frac{1}{9} - 0,3.\frac{5}{9} + \frac{1}{3}\\ = \frac{1}{9} - \frac{3}{{10}}.\frac{5}{9} + \frac{1}{3}\\ = \frac{1}{9} - \frac{3}{{2.5}}.\frac{5}{{3.3}} + \frac{1}{3}\\ = \frac{1}{9} - \frac{1}{6} + \frac{1}{3}\\ = \frac{2}{{18}} - \frac{3}{{18}} + \frac{6}{{18}}\\ = \frac{5}{{18}}\end{array}\)
b)
\(\begin{array}{l}{\left( {\frac{{ - 2}}{3}} \right)^2} + \frac{1}{6} - {\left( { - 0,5} \right)^3}\\ = \frac{4}{9} + \frac{1}{6} - \left( {\frac{{ - 1}}{2}} \right)^3\\ = \frac{4}{9} + \frac{1}{6} - \left( {\frac{{ - 1}}{8}} \right)\\ = \frac{4}{9} + \frac{1}{6} + \frac{1}{8}\\ = \frac{{32}}{{72}} + \frac{{12}}{{72}} + \frac{9}{{72}}\\ = \frac{{53}}{{72}}\end{array}\)
\(\left(\frac{2}{5}\right)^6.\left(\frac{25}{4}\right)^2\)
\(=\left[\left(\frac{2}{5}\right)^3\right]^2.\left(\frac{25}{4}\right)^2\)
\(=\left[\left(\frac{2}{5}\right)^3.\frac{25}{4}\right]^2\)
\(=\left[\frac{8}{125}.\frac{25}{4}\right]^2\)
\(=\left(\frac{2}{5}\right)^2\)
\(=\frac{4}{25}\)
\(15\frac{1}{5}:\left(\frac{-5}{7}\right)-25\frac{1}{5}.\left(\frac{-7}{5}\right)\)
\(=15\frac{1}{5}.\frac{-7}{5}-25\frac{1}{5}.\frac{-7}{5}\)
\(=\frac{-7}{5}\left(15\frac{1}{5}-25\frac{1}{5}\right)\)
\(=\frac{-7}{5}.\left(-10\right)\)
\(=14\)
1:
a: =7/5(40+1/4-25-1/4)-1/2021
=21-1/2021=42440/2021
b: =5/9*9-1*16/25=5-16/25=109/25
\(2^3+3.\left(\frac{2}{3}\right)^0-2+\left[\left(-2\right)^2:\frac{1}{2}\right]-8\)
đổi p/s \(\left(\frac{2}{3}\right)^0=1\)
xong tính trong ngoặc vuông,
r xử dụng tính chất phân phối
nhanh nha 4h30 mik hc r