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a: \(=2\cdot\dfrac{5}{4}-3\cdot\dfrac{7}{6}+4\cdot\dfrac{9}{8}=\dfrac{5}{2}-\dfrac{7}{2}+\dfrac{9}{2}=\dfrac{7}{2}\)
b: \(=18-16\cdot\dfrac{1}{2}+\dfrac{1}{16}\cdot\dfrac{3}{4}\)
=10+3/64
=643/64
c: \(=\dfrac{2}{3}\cdot\dfrac{9}{4}-\dfrac{3}{4}\cdot\dfrac{8}{3}+\dfrac{7}{5}\cdot\dfrac{5}{14}=\dfrac{3}{2}-2+\dfrac{1}{2}=2-2=0\)
\(M=1-\frac{5}{\sqrt{196}}-\frac{5}{\left(2\sqrt{21}\right)^2}-\frac{\sqrt{25}}{204}-\frac{\left(\sqrt{5}\right)^2}{374}\)
\(=1-\frac{5}{14}-\frac{5}{84}-\frac{5}{204}-\frac{5}{374}\left(\text{(}2\sqrt{21}\text{)}^2=2^2.21=84\right)\)
\(=1-\frac{5}{2.7}-\frac{5}{7.12}-\frac{5}{12.17}-\frac{5}{17.22}\)
\(=1-\frac{1}{2}+\frac{1}{7}-\frac{1}{7}+\frac{1}{12}-\frac{1}{12}+\frac{1}{17}-\frac{1}{17}+\frac{1}{22}\)
\(=1-\frac{1}{2}+\frac{1}{22}\)
\(=\frac{22-11+1}{22}=\frac{12}{22}=\frac{6}{11}\)
Vậy M = 6/11.
\(M=1-\dfrac{5}{14}-\dfrac{5}{84}-\dfrac{5}{204}-\dfrac{5}{374}\)
\(=\dfrac{84-30-5}{84}-\dfrac{5}{204}-\dfrac{5}{374}\)
\(=\dfrac{49}{84}-\dfrac{5}{204}-\dfrac{5}{374}\)
\(=\dfrac{7}{12}-\dfrac{5}{204}-\dfrac{5}{374}\)
\(=\dfrac{7\cdot17-5}{204}-\dfrac{5}{374}=\dfrac{19}{34}-\dfrac{5}{374}=\dfrac{204}{374}=\dfrac{6}{11}\)
Giải:
\(A=1-\dfrac{5}{\sqrt{196}}-\dfrac{5}{\left(2.\sqrt{21}\right)^2}-\dfrac{\sqrt{25}}{204}-\dfrac{\left(\sqrt{5}\right)^2}{374}\)
\(\Leftrightarrow A=1-\dfrac{5}{14}-\dfrac{5}{2^2.\left(\sqrt{21}\right)^2}-\dfrac{5}{204}-\dfrac{5}{374}\)
\(\Leftrightarrow A=1-\dfrac{5}{14}-\dfrac{5}{84}-\dfrac{5}{204}-\dfrac{5}{374}\)
\(\Leftrightarrow A=\dfrac{5}{5}-\dfrac{5}{14}-\dfrac{5}{84}-\dfrac{5}{204}-\dfrac{5}{374}\)
\(\Leftrightarrow A=5\left(\dfrac{1}{5}-\dfrac{1}{14}-\dfrac{1}{84}-\dfrac{1}{204}-\dfrac{1}{374}\right)\)
\(\Leftrightarrow A=5.\dfrac{6}{55}\)
\(\Leftrightarrow A=\dfrac{6}{11}\)
Vậy giá trị của biểu thức A là \(\dfrac{6}{11}\).
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