Ta có : \(\frac{4}{11}.\frac{-2}{9}+\frac{4}{11}\frac{-8}{9}+\frac{4}{11}.\frac{1}{9}\)

= \(\frac{4}{11}.\left(\frac{-2}{9}+\frac{-8}{9}+\frac{1}{9}\right)\)

= \(\frac{4}{11}.\frac{-9}{9}\)

= \(\frac{4}{11}.\left(-1\right)\)

= \(\frac{-4}{11}\)

\(\frac{4}{11}\left(-\frac{2}{9}+-\frac{8}{9}+\frac{1}{9}\right)=\frac{4}{11}1=\frac{4}{11}\)

xin lỗi =-4/11

\(\dfrac{-4}{3}-\dfrac{5}{7}+\dfrac{4}{3}=\left(\dfrac{4}{3}+\dfrac{-4}{3}\right)-\dfrac{5}{7}=0-\dfrac{5}{7}=-\dfrac{5}{7}\)

\(\dfrac{3}{13}\cdot\dfrac{6}{11}+\dfrac{3}{13}\cdot\dfrac{9}{11}-\dfrac{3}{13}\cdot\dfrac{4}{11}=\dfrac{3}{13}\cdot\left(\dfrac{6}{11}+\dfrac{9}{11}-\dfrac{4}{11}\right)=\dfrac{3}{13}\cdot1=\dfrac{3}{13}\)

Đặt : \(A=\dfrac{4}{8\times11}+\dfrac{4}{11\times14}+...+\dfrac{4}{296\times299}\)

\(\dfrac{3\times A}{4}=\dfrac{3}{8\times11}+\dfrac{3}{11\times14}+...+\dfrac{3}{296\times299}\\ =\dfrac{1}{8}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{14}+...+\dfrac{1}{296}-\dfrac{1}{299}\\ =\dfrac{1}{8}-\dfrac{1}{299}\\ A=\left(\dfrac{1}{8}-\dfrac{1}{299}\right)\times4:3=\dfrac{97}{598}\)

Ta đặt

\(A=\dfrac{4}{8\times11}+\dfrac{4}{11\times14}+....+\dfrac{4}{296\times299}\)

\(\dfrac{3}{4}A=\dfrac{3}{8\times11}+\dfrac{3}{11\times14}+....+\dfrac{3}{296\times299}\)

\(\dfrac{3}{4}A=\dfrac{1}{8}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{14}+....+\dfrac{1}{296}-\dfrac{1}{299}\)

\(\dfrac{3}{4}A=\dfrac{1}{8}-\dfrac{1}{299}=\dfrac{291}{2392}\)

\(A=\dfrac{291}{2392}\div\dfrac{3}{4}\)

\(A=\dfrac{97}{598}\)

bằng-12phần 77

-\(\frac{4}{11}\)nha

ket qua ra -4/11 nha ban

nhiều thế

sfdhg 

Đặt A=4/9x11+4/11x13+4/13x15+..+4/97x99

A=2x( 2/9x11+2/11x13+...+2/97x99)

A=2x(1/9-1/11+1/11-1/13+...+1/97-1/99)

A=2x(1/9-1/99)

A=2x10/99=20/99

yêu cầu là tính phải ko bn ( lần sau nhớ ghi rõ yêu cầu nhé !) 

Đặt A=4/9x11+4/11x13+4/13x15+...+4/97x99

A=2x(2/9x11+2/11x13+...+2/97x99)

A=2x(1/9-1/11+1/11-1/13+...+1/97-1/99)

A=2x(1/9-1/99) 

A=2x10/99=20/99

\(=2\left(\frac{1}{9}-\frac{1}{11}+\frac{1}{11}-\frac{1}{13}+...+\frac{1}{97}-\frac{1}{99}\right)\)

\(=2\left(\frac{1}{9}-\frac{1}{99}\right)\)

\(=2.\frac{10}{99}\)

\(=\frac{20}{99}\)

\(4.3^{x-1}+2.3^{x+2}=4.3^6+2.3^9\)

\(3^{x-1}.\left(4+2.3^3\right)=3^6.\left(4+2.3^3\right)\)

\(\Leftrightarrow3^{x-1}=3^6\)

\(\Leftrightarrow x-1=6\)

\(\Leftrightarrow x=7\)

Vậy \(x=7\)

\(5^{x+4}-3.5^{x+3}=2.5^{11}\)

\(\Leftrightarrow5^{x+3}.\left(5-3\right)=2.5^{11}\)

\(\Leftrightarrow5^{x+3}.2=2.5^{11}\)

\(\Leftrightarrow5^{x+3}=5^{11}\)

⇔\(x+3=11\)

\(\Leftrightarrow x=8\)

Vậy \(x=8\)

\(11.6^{x-1}=11.6^{11}+2.6^{13}\)

\(\Rightarrow11.6^{x-1}=6^{11}.\left(11+2.36\right)\)

\(\Rightarrow11.6^{x-1}=6^{11}.83\)

\(-\frac{7}{11}.\frac{11}{19}+\frac{-7}{11}.\frac{8}{19}+\frac{-4}{11}=-\frac{7}{11}.\left(\frac{11}{19}+\frac{8}{19}\right)-\frac{4}{11}\)

\(=-\frac{7}{11}.1-\frac{4}{11}=-\frac{7}{11}-\frac{4}{11}\)

\(=-\frac{11}{11}=-1\)