Bn nào nhanh và đúng mình k cho nhé. 

Là k ko phải k ( đánh lộn)

a: \(=\left(5^2+3\right):7=4\)

b: \(=7^2-3^2+8\cdot25=40+200=240\)

Còn C ai làm ko ạ

37.39+78+37.39

=37.39 .(1+1)+78

=37.39.2+78

=37.78+78

=78.(37+1)=78.38=2964

\(a,=600+72+18=690\\ b,=25+5-20=10\\ c,=45-28+83=100\\ d,=25+36+1=62\\ e,=151-8+3=146\)

a)600+72+18=690

b)25+5-20=10

c)45-28+83=100

d)25+36+1=62

e)151-8+3=146

`A=4/[5.7]+4/[7.9]+4/[9.11]+...+4/[21.23]+4/[23.25]`

`A=2.(2/[5.7]+2/[7.9]+....+2/[23.25])`

`A=2.(1/5-1/7+1/7-1/9+....+1/23-1/25)`

`A=2.(1/5-1/25)`

`A=2. 4/25`

`A=8/25`

\(2B=2\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{23}-\frac{1}{25}\right)\)

\(2B=2\left(\frac{1}{3}-\frac{1}{25}\right)\)

\(2B=2\times\frac{22}{75}\)

\(B=\frac{44}{75}\)

\(=\frac{23^{10}\left(1-23\right)}{23^{10}\left(23+21\right)}=\frac{-22}{44}=\frac{-1}{2}\)

\(\frac{23^{10}-23^{11}}{23^{11}+21.23^{10}}\)

\(=\frac{23^{10}.\left(1-23\right)}{23^{10}.\left(23+21\right)}\)

\(=\frac{-22}{44}=\frac{-22}{22.2}=\frac{-1}{2}\)

\(A=\dfrac{1}{1.2}+\dfrac{1}{2.3}+...+\dfrac{1}{49.50}\)

\(A=\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{49}-\dfrac{1}{50}\)

\(A=\dfrac{1}{1}-\dfrac{1}{50}=\dfrac{49}{50}\)

\(A=\dfrac{1}{1.2}+\dfrac{1}{2.3}+...+\dfrac{1}{49.50}=\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{49}-\dfrac{1}{50}\)

\(A=\dfrac{1}{1}-\dfrac{1}{50}=\dfrac{50}{50}-\dfrac{1}{50}=\dfrac{49}{50}\)

A=\(\dfrac{2}{1.3}-\dfrac{2}{3.5}-\dfrac{2}{5.7}-.....-\dfrac{2}{23.25}-\dfrac{1}{27}\)

A=\(\dfrac{2}{3}-\left(\dfrac{2}{3.5}+\dfrac{2}{5.7}+....+\dfrac{2}{23.25}\right)-\dfrac{1}{27}\)

A=\(\dfrac{2}{3}-\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+......+\dfrac{1}{23}-\dfrac{1}{25}\right)-\dfrac{1}{27}\)

A=\(\dfrac{2}{3}-\left(\dfrac{1}{3}-\dfrac{1}{25}\right)-\dfrac{1}{27}\)

A=\(\dfrac{2}{3}-\dfrac{22}{75}-\dfrac{1}{27}\)

A=\(\dfrac{227}{675}\)

đề sai rùi bn ơi, đáng ra phải là: 53.39+37.39....... mới đúng

kết quả là 4200