Trl :

= 25/53 nha bn

#hoc_tot#

:>

252525 / 535353 = 25 x 10101 / 53 x 10101 = 25 / 53

b: \(\frac{4^6\cdot9^5+6^9\cdot120}{8^4\cdot3^{12}-6^{11}}\)

\(=\frac{2^{12}\cdot3^{10}+2^9\cdot3^9\cdot2^3\cdot3\cdot5}{2^{12}\cdot3^{12}-2^{11}\cdot3^{11}}\)

\(=\frac{2^{12}\cdot3^{10}\left(1+5\right)}{2^{11}\cdot3^{11}\left(2\cdot3-1\right)}=\frac23\cdot\frac65=\frac{12}{15}=\frac45\)

c: \(\frac{7\cdot28^8+2^4\cdot14^{10}}{4^4\cdot14^9-70\cdot16^3\cdot49^4}\)

\(=\frac{7\cdot7^8\cdot2^{16}+2^4\cdot2^{10}\cdot7^{10}}{2^8\cdot2^9\cdot7^9-2\cdot5\cdot7\cdot2^{12}\cdot7^8}=\frac{7^9\cdot2^{14}\left(2^2+7\right)}{2^{13}\cdot7^8\left(2^4-5\cdot7\right)}=\frac{7\cdot2\cdot\left(4+7\right)}{16-35}=\frac{14\cdot11}{-19}=\frac{-154}{19}\)

\(\dfrac{121\times75\times130\times169}{39\times60\times11\times198}\)

\(=\dfrac{25\times169}{6\times18}\)

\(=\dfrac{4225}{108}\)

668068830000

= 199377750/5096520

=4225/108

Kết quả là 39/76

ket qua la:39/76

H = 10/56 + 10/140 + 10/260 + ... + 10/1400

H = 5/3 × (3/28 + 3/70 + 3/130 + ... + 3/700)

H = 5/3 × (3/4×7 + 3/7×10 + 3/10×13 + ... + 3/25×28)

H = 5/3 × (1/4 - 1/7 + 1/7 - 1/10 + 1/10 - 1/13 + ... + 1/25 - 1/28)

H = 5/3 × (1/4 - 1/28)

H = 5/3 × 3/14

H = 5/14

\(H=\frac{10}{56}+\frac{10}{140}+\frac{10}{260}+....+\frac{10}{1400}\)

   \(=\frac{5}{4.7}+\frac{5}{7.10}+\frac{5}{10.13}+....+\frac{5}{25.28}\)

   \(=\frac{5}{3}.\left(\frac{3}{4.7}+\frac{3}{7.10}+\frac{3}{10.13}+....+\frac{3}{25.28}\right)\)

    \(=\frac{5}{3}.\left(\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+....+\frac{1}{25}-\frac{1}{28}\right)\)

     \(=\frac{5}{3}.\left(\frac{1}{4}-\frac{1}{28}\right)\)

     \(=\frac{5}{3}.\frac{3}{14}=\frac{5}{14}\)

4.

tử của A= 4(1.2 + 2.4+...+8.10) 

mẫu của A= 1.2 + 2.4+...+8.10 nên A=4