U_U lớp 6 

B=1+2+2²+2³+....+2²⁰⁰⁸/1-2²⁰⁰⁹

2B=1+2+2²+2³+...+2²⁰⁰⁹/1-2²⁰⁰⁹

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

B=1-2²⁰⁰⁹/1-2²⁰⁰⁹

B=1

\(=\frac{-34\left(15-2\right)}{13.68}\)

\(=\frac{-34.13}{13.68}\)

\(=-\frac{34}{68}=-\frac{1}{2}\)

Trả lời:

=\(\frac{43\left(2-15\right)}{13.68}\)=\(\frac{43.\left(-13\right)}{13.68}\)=-\(\frac{43}{68}\)

\(=\frac{2}{3}+\frac{2}{7}\)

\(=\frac{20}{21}\)

Cảm ơn bạn

\(A=\frac{-1}{20}+\frac{-1}{30}+\frac{-1}{42}+\frac{-1}{56}+\frac{-1}{72}+\frac{-1}{90}\)

\(A=-\left(\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}\right)\)

\(A=-\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\right)\)

\(A=-\left(\frac{1}{4}-\frac{1}{10}\right)\)

\(A=-\frac{3}{20}\)

#H

=-1/20-(1/30+1/42+1/56+1/72+1/90)

=-1/20-(1/5.6+1/6.7+1/7.8+1/8.9+1/9.10)

=-1/20-(1/5-1/6+1/6-1/7+....+1/9-1/10)

=-1/20-(1/5-1/10)

=-1/20-1/10=-3/20

\(\Leftrightarrow2x-x=-25+5\)

\(\Leftrightarrow x=-20\)

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

\(x-\frac{150}{3}=-23\)

\(x-50=-23\)

\(x=27\)

Vậy:...

#H

|x-8|+12=25

B= 2^2009-1/1+2^2009

(-5)³ - [65-(7-3)²]

=-125-[65-16]

=-125-49

=-174

#H

\(\left(-5\right)^3-\left[65-\left(7-3\right)^2\right]\)

\(=\left(-125\right)-\left(65-4^2\right)\)

\(=\left(-125\right)-\left(65-16\right)\)

\(=\left(-125\right)-49\)

\(=\left(-174\right)\)

\(\left(\frac{5}{7}-\frac{1}{8}\right)-\left(\frac{7}{8}-\frac{10}{7}\right)\)

\(=\frac{5}{7}-\frac{1}{8}-\frac{7}{8}+\frac{10}{7}\)

\(=\left(\frac{5}{7}+\frac{10}{7}\right)+\left(-\frac{1}{8}-\frac{7}{8}\right)\)

\(=\frac{15}{7}-1\)

\(=\frac{8}{7}\)

#H

cảm ơn nhiều bạn