`2/5 - 3/8 + 7/6 : 7/5`

`= 2/5 - 3/8 + 7/6 xx 5/7`

`= 2/5 - 3/8 +5/6`

`= 1/40+5/6`

`=103/120`

2S = 2 + 2^2 + 2^3 + ...+ 2^64

2S + 1 = 1 + 2 + 2^2 + ... + 2^64

2S - S = 2^64 - 1

Vậy S =  2^64 - 1

\(A=2^2+2^3+...+2^{62}+2^{63}\)

\(2A=2^3+2^4+...+2^{63}+2^{64}\)

\(2A-A=\left(2^3+2^4+...+2^{63}+2^{64}\right)-\left(2^2+2^3+...+2^{62}+2^{63}\right)\)

\(A=2^{64}-2^2\)

2S = 2 + 2^2 + 2^3 + ...+ 2^64

2S + 1 = 1 + 2 + 2^2 + ... + 2^64

2S - S = 2^64 - 1

Vậy S =  2^64 - 1

k mk

mình cần gấp giúp mình với

3^x x 2 + 15 = 33

<=> 3^x = 9

<=> x = 2

3^x . 2 + 15 = 33

3^x . 2 = 33 - 15 = 18

3^x = 18 : 2 = 9 = 3²

=> x = 2

\(3^x.2+15=33\)

\(< =>3^x.2=33-15=18\)

\(< =>3^x=18:2=9\)

\(< =>x=2\)

=(1-2)-(3-4)+(5-6)-(7-8)+...+(2021-2022)-2023
=(-1)-(-1)+(-1)-...+(-1)-2023
=0-2023
=-2023

Kết quả là 105/70 = 3/2

Chúc bn học tốt

\(2S=\frac{2}{1}-\frac{2}{3}+\frac{2}{3}-\frac{2}{5}+...+\frac{2}{97}-\frac{2}{99}\)

\(2S=2-\frac{2}{99}\)

\(2S=\frac{196}{99}\)

\(S=\frac{196}{99}\cdot\frac{1}{2}=\frac{98}{99}\)

Ta có: S=2/1.3+2/3.5+...+2/97.99

S= 2/2.(1-1/3+1/3-1/5+...+1/97-1/99)

S= 1-1/99=98/99

\(S=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{97.99}\)

\(2S=2\left(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{97.99}\right)\)

\(\Rightarrow S=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{97}-\frac{1}{99}\)

\(S=1-\frac{1}{99}\)

\(S=\frac{98}{99}\)