\(A=\frac{-5}{7}+\frac{3}{4}+\frac{-1}{5}+\frac{-2}{7}+\frac{1}{4}\)

\(A=\left(\frac{-5}{7}+\frac{-2}{7}\right)+\left(\frac{3}{4}+\frac{1}{4}\right)+\frac{-1}{5}\)

\(A=-1+1+\frac{-1}{5}\)

\(A=\frac{-1}{5}\)

\(B=\frac{-4}{12}+\frac{18}{45}+\frac{-6}{9}+\frac{-21}{35}+\frac{6}{30}\)

\(B=\frac{-1}{3}+\frac{2}{5}+\frac{-2}{3}+\frac{-3}{5}+\frac{1}{5}\)

\(B=\left(\frac{-1}{3}+\frac{-2}{3}\right)+\left(\frac{2}{5}+\frac{-3}{5}+\frac{1}{5}\right)\)

\(B=-1+0\)

\(B=-1\)

-4/12 + 18/45 - 6/9 - 21/35 + 6/30

= -1/3 + 2/5 - 2/3 - 3/5 + 1/5

= (2/5 - 3/5 + 1/5) - (1/3 + 2/3)

= 0 - 1

= -1

\(=-\frac{1}{3}+\frac{2}{5}-\frac{2}{3}-\frac{3}{5}+\frac{1}{5}\)

\(=\left(-\frac{1}{3}-\frac{2}{3}\right)+\left(\frac{2}{5}-\frac{3}{5}+\frac{1}{5}\right)\)

\(=-1+0\)

\(=-1\)

=.= hk tốt!!

\(B=-\frac{1}{3}+\frac{2}{5}-\frac{2}{3}-\frac{3}{5}+\frac{1}{5}\)

\(=\left(-\frac{1}{3}-\frac{2}{3}\right)+\left(\frac{2}{5}-\frac{3}{5}+\frac{1}{5}\right)\)

\(=-\frac{3}{3}+0\)

\(=-1\)

=.= hk tốt!!

B=\(\frac{-4}{12}+\frac{18}{45}+\frac{-6}{9}+\frac{-21}{35}+\frac{6}{30}\)

  =\(\frac{-4}{4\cdot3}+\frac{2\cdot9}{5\cdot9}+\frac{\left(-2\right)\cdot3}{3\cdot3}+\frac{\left(-4\right)\cdot7}{5\cdot7}+\frac{6}{5\cdot6}\)

  =\(\frac{-1}{3}+\frac{2}{5}+\frac{-2}{3}+\frac{-4}{5}+\frac{1}{5}\)

  = \(\left(\frac{-1}{3}+\frac{-2}{3}\right)+\left(\frac{-4}{5}+\frac{2}{5}+\frac{1}{5}\right)\)

  =\(\frac{-3}{3}+\frac{-1}{5}\)

  = \(-1+\frac{-1}{5}\)=\(\frac{-5-1}{5}=\frac{-6}{5}\)

\(=\frac{9^{15}.6^{30}}{27^{21}.8^{11}}\)

\(=\frac{\left(3^2\right)^{15}.3^{30}.2^{30}}{\left(3^3\right)^{21}.\left(2^3\right)^{11}}\)

\(=\frac{3^{30}.3^{30}.2^{30}}{3^{63}.2^{33}}\)

\(=\frac{3^{60}.2^{30}}{2^{63}.3^{33}}=\frac{1}{2^3.3^3}=\frac{1}{216}\)

làm mẫu một bài còn lại tương tự nha bn =)

\(\frac{9^{15}.6^{30}}{27^{21}.8^{11}}=\frac{\left(3^2\right)^{15}.\left(2.3\right)^{30}}{\left(3^3\right)^{21}.\left(2^3\right)^{11}}=\frac{3^{60}.2^{30}}{3^{63}.2^{33}}=\frac{1}{3^3.2^3}\)

\(\frac{45^{12}.49^7}{35^{13}.27^8}=\frac{\left(5.3^2\right)^{12}.\left(7^2\right)^7}{\left(5.7\right)^{13}.\left(3^3\right)^8}=\frac{5^{12}.3^{24}.7^{14}}{5^{13}.7^{13}.3^{24}}=\frac{7}{5}\)

#

\(\frac{9^{15}\cdot6^{30}}{27^{21}\cdot8^{11}}=\frac{\left(3^2\right)^{15}\cdot\left(2\cdot3\right)^{30}}{\left(3^3\right)^{21}\cdot\left(2^3\right)^{11}}=\frac{3^{30}\cdot2^{30}3^{30}}{3^{63}\cdot2^{33}}=\frac{3^{60}\cdot1}{3^{63}\cdot2^3}=\frac{1}{27\cdot8}=\frac{1}{216}\)

\(\frac{45^{12}\cdot49^7}{35^{13}\cdot27^8}=\frac{\left(3^2\cdot5\right)^{12}\left(7^2\right)^7}{\left(5\cdot7\right)^{13}\left(3^3\right)^8}=\frac{3^{24}\cdot5^{12}\cdot7^{14}}{5^{13}\cdot7^{13}\cdot3^{24}}=\frac{1\cdot1\cdot7}{5\cdot1\cdot1}=\frac{7}{5}\)

giúp với ạ

giải dc nhưng mà hoi lâu

a)\(\dfrac{5}{7}+\dfrac{4}{9}=\dfrac{45}{63}+\dfrac{28}{63}=\dfrac{73}{63}\) ; \(\dfrac{9}{11}+\dfrac{3}{8}=\dfrac{72}{88}+\dfrac{33}{88}=\dfrac{105}{88}\)

\(\dfrac{4}{5}-\dfrac{2}{3}=\dfrac{12}{15}-\dfrac{10}{15}=\dfrac{2}{15}\); \(\dfrac{16}{25}-\dfrac{2}{5}=\dfrac{16}{25}-\dfrac{10}{25}=\dfrac{6}{25}\)

đáp án:251/30 

k cho mk nha

\(a.\frac{27.45+27.55}{2+4+6+...+14+16+18}=\frac{27.100}{\frac{\left(2+18\right).9}{2}}=30\)

\(b.\frac{26.108-26.12}{32-28+24-20+16-12+8-4}=\frac{26\left(108-12\right)}{\left(32-28\right).4}=\frac{26.96}{4.4}=156\)

\(c.\frac{27.4500+135.550.2}{2+4+6+...+14+16+18}=\frac{270.450+270.550}{\frac{\left(2+8\right).9}{2}}\)

\(d.\frac{48.700-24.45.20}{45-40+35-30+25-20+15-10+5}=\frac{48.700-48.450}{5.5}\)\(=\frac{48\left(700-450\right)}{25}=\frac{48.250}{25}=480\)

#ĐinhBa