ra 33737/5 bạn ạ

bạn chi mk cách làm đc ko

a/ =-12.916

b=6747/2/5

k nha

\(\frac{-3}{5}+\frac{28.43}{5.56}+\frac{28.5}{5.24}-\frac{28.21}{5.63}\)

=\(\frac{-3}{5}+\frac{2.2.7.43}{5.2.2.7.2}+\frac{2.2.7.5}{2.2.2.3.5}-\frac{2.2.7.3.7}{5.7.3.3}\)

=\(\frac{-3}{5}+\frac{43}{5.2}+\frac{7}{2.3}-\frac{28}{15}\)

=\(\frac{-3}{5}+\frac{43}{10}+\frac{7}{6}-\frac{28}{15}\)

=\(\frac{-18}{30}+\frac{129}{30}+\frac{35}{30}-\frac{56}{30}\)

=\(\frac{-18+129+35-56}{30}\)

=\(\frac{90}{30}=3\)

Chúc bn học tốt

tự làm đê đồ đầu đất

a)=16.5-[131-(13-16)]

=80-[131--3] 

=80-134=-54

b

.ta có 

=-3/5+28/5.43/56+28/5.5/24-28/5.21/63 

=-3/5+28/5.(43/56+5/24-21/63)

=5.9/14=45/14

suy ra 

biểu thức b có giá trị là 45/14

mk nghĩ bn nê thử tách 28.43/5.56 và 28.21/5.63 ra thành 28/5.43/56 và 28/5.21/63 để có phân số chung, mk sợ sai nên bn cứ thử lm r tự tính tiếp nha

-3/5 + 28.43/5.56 + 28.5/5.24 - 28.21/5.63

=-3/5 + 28.43/5.28.2 + 4.7.5/5.4.6 - 28.21/5.3.21

=-3/5 + 43/10 + 7/6 - 28/15

=-18/30 + 129/30 + 35/30 - 56/30

=-12+129+35-56/30

=94/30=47/15

Bạn có thể tự bấm máy nhé:

A=\(\left(\dfrac{5}{2}-\dfrac{2}{5}+\dfrac{1}{10}\right):\left(\dfrac{5}{2}-\dfrac{2}{3}+\dfrac{1}{32}\right)\)

\(\Rightarrow A=\dfrac{11}{5}:\dfrac{179}{96}=\dfrac{11}{5}.\dfrac{96}{179}=\dfrac{1056}{895}\)

Chúc bạn học tốt!

\(\dfrac{1}{1}+\dfrac{1}{3}+\dfrac{1}{9}+...+\dfrac{1}{729}\\ =\dfrac{1}{1}+\dfrac{1}{3}+\dfrac{1}{3^2}+...+\dfrac{1}{3^6}\\ =\dfrac{3-1}{2}\cdot\left(\dfrac{1}{1}+\dfrac{1}{3}+\dfrac{1}{3^2}+...+\dfrac{1}{3^6}\right)\\ =\dfrac{\left(3-1\right)\left(\dfrac{1}{1}+\dfrac{1}{3}+\dfrac{1}{3^2}+...+\dfrac{1}{3^6}\right)}{2}\\ =\dfrac{3-1+1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{3^2}+...+\dfrac{1}{3^5}-\dfrac{1}{3^6}}{2}\\ =\dfrac{3-\dfrac{1}{3^6}}{2}\\ =\dfrac{\dfrac{3^7}{3^6}-\dfrac{1}{3^6}}{2}\\ =\dfrac{2187-1}{729}\cdot\dfrac{1}{2}\\ =\dfrac{2186}{729}\cdot\dfrac{1}{2}\\ =\dfrac{1093}{729}\)

Đặt biểu thức là P , theo bài ra ta có:

\(\dfrac{1}{3}P=\dfrac{1}{3}+\dfrac{1}{3^2}+.......+\dfrac{1}{3^6}+\dfrac{1}{3^7}\)

\(=>P-\dfrac{1}{3}P=\left(1-\dfrac{1}{3^7}\right)\)

\(=>\dfrac{2}{3}P=\dfrac{2186}{2187}\)

\(=>P=\dfrac{2186}{2187}:\dfrac{2}{3}=\dfrac{1093}{729}\)

CHÚC BẠN HỌC TỐT.......

Đặt biểu thức là A , theo đề bài ta có

\(\dfrac{1}{3}A=\dfrac{1}{3}+\dfrac{1}{3^2}+..+\dfrac{1}{3^6}+\dfrac{1}{3^7}\)

=> \(\dfrac{1}{3}A-A=\left(1-\dfrac{1}{3^7}\right)\)

=> \(\dfrac{2}{3}A=\dfrac{2186}{2187}=>A=\dfrac{2186}{2187}:\dfrac{2}{3}=\dfrac{1093}{729}\)

Vậy A = \(\dfrac{1093}{729}\)

\(\dfrac{1}{x^2+x+1}-\dfrac{1}{x-x^2}-\dfrac{x^2+2x}{x^3-1}\)

\(=\dfrac{\left(x-1\right)x}{x\left(x-1\right)\left(x^2+x+1\right)}+\dfrac{x^2+x+1}{x\left(x-1\right)\left(x^2+x+1\right)}-\dfrac{\left(x^2+2x\right)x}{x\left(x-1\right)\left(x^2+x+1\right)}\)

\(=\dfrac{x^2-x+x^2+x+1-x^3-2x^2}{x\left(x-1\right)\left(x^2+x+1\right)}\)

\(=\dfrac{1-x^3}{x\left(x-1\right)\left(x^2+x+1\right)}\)

\(=\dfrac{-\left(x^3-1\right)}{x\left(x^3-1\right)}=\dfrac{-1}{x}\)