2B=2+2^2+2^3+......+2²⁰⁰⁹

2B-B=2²⁰⁰⁹-1

2B=2+2^2+2^3+......+2²⁰⁰⁹

2B-B=2²⁰⁰⁹-1

B

đặt tử là A,ta có:

2A=2(1+2+2²+2³+...+2²⁰⁰⁸)

2A=2*1+2*2+2*2²+...+2*2²⁰⁰⁸

2A=2+2²+2³+...+2²⁰⁰⁹

2A-A=(2+2²+2³+...+2²⁰⁰⁹)-(1+2+2²+...+2²⁰⁰⁸)

A=2²⁰⁰⁹-1

thay A vào tử số ta được \(B=\frac{2^{2009}-1}{1-2^{2009}}=-1\)

25-[50-(2^3.17-2^3.14)]

=25-[50-(8.17-8.14)]

=25-[50-(136-112)]

=25-[50-24]

=25-26

=-1

|-128|: [45^2-(2010-2008.1^2010)]

=128:[45^2-(2010-2008.1)]

=128:[45^2-(2010-2008)]

=128:[45^2-2]

=128:[2025-2]

=128:2023

=0,063 (chắc mik làm sai b đấy :(  )

25-[50-(2^3.17-2^3.14)]=25-{50-[2^3.(17-14)]}

                                     =25-{50-[8.3]}

                                     =25-{50-24}

Ta co:\(B=\frac{2008}{1}+\frac{2007}{2}+...+\frac{2}{2007}+\frac{1}{2008}\)

           \(B=\frac{2009-1}{1}+\frac{2009-2}{2}+...+\frac{2009-2007}{2007}+\frac{2009-2008}{2008}\)

            \(B=\left(\frac{2009}{1}+\frac{2009}{2}+...+\frac{2009}{2008}\right)-\left(\frac{1}{1}+\frac{2}{2}+...+\frac{2008}{2008}\right)\)

            \(B=2009+2009\left(\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2008}\right)-2008\)

            \(B=1+2009\left(\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2008}\right)\)

             \(B=2009\left(\frac{1}{2}+\frac{1}{3}+....+\frac{1}{2008}+\frac{1}{2009}\right)\)

Vay \(\frac{A}{B}=\frac{1}{2009}\)

mik đọc nhầm đề rồi.Kết quả là 9/187

Li-ke cho mik nhé!

a )10 + 5/4 = 45,4

Đáp số : 45,4

\(\frac{10+5}{4.5}=\frac{15}{20}=\frac{3}{4}\)

\(\frac{2^2.9}{27.3}=\frac{4.9}{27.3}=\frac{36}{81}=\frac{4}{9}\)

k mk nha!!!