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Lời giải:
Gọi phân số trên là $A$. Ta có:
$A=\frac{12,48:6,48\times 2\times 8\times 6,25\times 3,25\times 4\times 4\times 2}{3,12\times 21,6\times 1,25\times 2,6\times 4\times 4\times 10\times 10}$
$=\frac{12,48:6,48\times (2\times 6,25)\times (8\times 3,25)\times 2}{3,12\times 21,6\times (1,25\times 10)\times (2,6\times 10)}$
$=\frac{12,48:6,48\times 12,5\times 26\times 2}{3,12\times 21,6\times 12,5\times 26}$
$=\frac{12,48:6,48\times 2}{3,12\times 21,6}=\frac{125}{2187}$
\(\frac{1}{11\times16}+\frac{1}{16\times21}+\frac{1}{21\times26}+...+\frac{1}{56\times61}+\frac{1}{61\times66}\)
\(=\frac{1}{5}\times\left(\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+\frac{1}{21}-\frac{1}{26}+...+\frac{1}{56}-\frac{1}{61}+\frac{1}{61}-\frac{1}{66}\right)\)
\(=\frac{1}{5}\times\left(\frac{1}{11}-\frac{1}{66}\right)\)
\(=\frac{1}{5}\times\frac{5}{66}\)
\(=\frac{1}{66}\)
\(\frac{1}{11\times16}+\frac{1}{16\times21}+\frac{1}{21\times26}+...+\frac{1}{56\times61}+\frac{1}{61\times66}\)
\(=\frac{1}{5}\times\left(\frac{5}{11\times16}+\frac{5}{16\times21}+\frac{5}{21\times26}+...+\frac{5}{56\times61}+\frac{5}{61\times66}\right)\)
\(=\frac{1}{5}\times\left(\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+\frac{1}{21}-\frac{1}{26}+...+\frac{1}{56}-\frac{1}{61}+\frac{1}{61}-\frac{1}{66}\right)\)
\(=\frac{1}{5}\times\left(\frac{1}{11}-\frac{1}{66}\right)\)
\(=\frac{1}{5}\times\frac{5}{66}=\frac{1}{66}\)
\(\Rightarrow15,6\div x=0,9+4,3=5,2\)
\(\Rightarrow x=15,6\div5,2=3\)
Vậy x = 3 nhé
Mình nhanh nhất!!!
đặt A= dãy số trên.Ta có:
5A= \(\frac{5}{11x16}+\frac{5}{16x21}+...+\frac{5}{61x66}\)
=> 5A= \(\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+...+\frac{1}{61}-\frac{1}{66}\)
=> 5A = \(\frac{1}{11}-\frac{1}{66}\)
=> 5A= \(\frac{5}{66}\)
=> A=\(\frac{1}{66}\)
\(=\frac{1}{5}\left(\frac{5}{11.16}\frac{5}{16.21}\frac{5}{21.26}+......+\frac{5}{61.66}\right)\)
\(=\frac{1}{5}\left(\frac{1}{11}-\frac{1}{16}+\frac{1}{16}-\frac{1}{21}+....+\frac{1}{61}+\frac{1}{66}\right)\)
=\(\frac{1}{5}\left(\frac{1}{11}+\frac{1}{66}\right)\)
\(=\frac{1}{5}.\frac{7}{66}\)
\(=\frac{7}{330}\)
15,6 x 260 - 156 x 26=0
15,6 x 3,3 x 3,4 x 2,6= 455,0832
=15,6 x10 x26 -156 x 26 / 15,6 x 3,3 x 3,4 x 2,6
=156 x 26 - 156 x 26 /
=0 / 15,6 x 3,3 x 3,4 x 2,6
=0
\(9:\frac{3}{5}\cdot\frac{4}{15}=\frac{3}{5}\cdot\frac{4}{15}=\frac{4}{25}\)
\(\frac{156}{6}=26\)
=\(\frac{15.6x26x10-15.6x10x26}{15.6x3.3x3.4x2.6}\)
=\(\frac{0}{15.6x3.3x3.4x2.6}\)
=0