=>36/18>x>8/15

=>2>x>8/15

mà x nguyên

nên x=1

\(\frac{2}{5}\cdot\frac{1}{2}-\frac{2}{5}\cdot\frac{1}{3}-\frac{2}{5}\cdot\frac{1}{6}\)

\(=\frac{2}{5}\cdot\left(\frac{1}{2}-\frac{1}{3}-\frac{1}{6}\right)\)

\(=\frac{2}{5}\cdot0=0\)

\(\frac{19}{11}+\left(\frac{8}{13}+\frac{3}{11}\right)\)

\(=\frac{19+3}{11}+\frac{8}{13}\)

\(=2+\frac{8}{13}=\frac{34}{13}\)

\(1,5+2\frac{3}{5}+\frac{4}{7}\)

\(=\frac{3}{2}+\frac{13}{5}+\frac{4}{7}\)

\(=\frac{327}{70}\)

\(x-\frac{5}{4}=6\cdot\frac{5}{8}\)

\(x-\frac{5}{4}=\frac{15}{4}\)

\(x=\frac{15}{4}+\frac{5}{4}\)

\(x=\frac{15+5}{4}=\frac{20}{4}=5\)

\(x\div2\frac{3}{4}=5\frac{2}{3}\)

\(x=5\frac{2}{3}\cdot2\frac{3}{4}\)

\(x=\frac{187}{12}\)

\(\frac{2}{3}\div x=\frac{3}{4}\)

\(x=\frac{2}{3}\div\frac{3}{4}\)

\(x=\frac{8}{9}\)

0, 75 = 3/4

Hiệu số phần bằng nhau là:

4 - 3 = 1

Số bé là:

0, 75 : 1 x 3 = 2, 25

Số lớn là:

2, 25 + 0, 75 = 3

Đ/s: ...

Trung bình cộng của 3 số là:

6045 : 3 = 2015

=> Số thứ 2 là 2015

Số thứ nhất là:

2015 - 1 = 2014

Số thứ 3 là:

2015 + 1 = 2016

Đ/s: ... 

x - 5/4 = 6 . 5/8

x - 5/4 = 15/4

x         = 15/4 + 5/4

x         = 5

\(x-\frac{5}{4}=6.\frac{5}{8}\)                                 \(x:2\frac{3}{4}=5\frac{2}{3}\)

\(x-\frac{5}{4}=\frac{15}{4}\)                                \(x:\frac{11}{4}=\frac{17}{3}\)

\(x=\frac{15}{4}+\frac{5}{4}\)                                 \(x=\frac{17}{3}.\frac{11}{4}\)

\(x=\frac{20}{4}=5\)                                      \(x=\frac{187}{12}\)

1 

\(\left(x-2\right):2.3=6\)

\(\Leftrightarrow\left(x-2\right):2=2\)

\(\Leftrightarrow\left(x-2\right)=4\)

\(\Leftrightarrow x=4+2=6\)

c) ta có

\(\left[\left(2x+1\right)+1\right]m:2=625\)

\(\Leftrightarrow\left[\left(2x+1\right)+1\right]\left\{\left[\left(2x+1\right)-1\right]:2+1\right\}=1250\)

\(\Leftrightarrow\left(2x+1\right)^2+1-1:2+1=1250\)

\(\Leftrightarrow\left(2x+1\right)^2+1-2+1=1250\)

\(\Leftrightarrow\left(2x+1\right)^2+1-2=1249\)

\(\Leftrightarrow\left(2x+1\right)^2+1=1251\)

\(\Leftrightarrow\left(2x+1\right)^2=1250\)

...

2

\(\left(x-\frac{1}{2}\right).\frac{5}{3}=\frac{7}{4}-\frac{1}{2}\)

\(\Leftrightarrow\left(x-\frac{1}{2}\right).\frac{5}{3}=\frac{5}{4}\)

\(\Leftrightarrow\left(x-\frac{1}{2}\right)=\frac{5}{4}:\frac{5}{3}\)

\(\Leftrightarrow\left(x-\frac{1}{2}\right)=\frac{5}{4}.\frac{3}{5}\)

\(\Leftrightarrow x-\frac{1}{2}=\frac{3}{4}\)

\(\Leftrightarrow x=\frac{3}{4}+\frac{1}{2}=\frac{5}{4}\)

BÀI 1:

         \(541-\left(125-x\right)\times2\frac{2}{3}=469\)

        \(\Rightarrow541-\left(125-x\right)\times\frac{8}{3}=469\)

         \(\Rightarrow541-\frac{1000}{3}+\frac{8}{3}\times x=469\)

          \(\Rightarrow\frac{623}{3}-\frac{8}{3}\times x=469\)

          \(\Rightarrow\frac{8}{3}\times x=\frac{784}{3}\)

           \(\Rightarrow x=98\)

BÀI 2 : 

       \(A=\frac{1}{2\times3}+\frac{1}{2\times3\times4}+\frac{1}{3\times4\times5}+...\)\(+\frac{1}{18\times19\times20}\)

            \(=\frac{1}{2}\times\left(\frac{1}{1\times2}+\frac{1}{2\times3}\right)+\frac{1}{2}\times\left(\frac{1}{2\times3}+\frac{1}{3\times4}\right)\)\(+...+\frac{1}{2}\times\left(\frac{1}{18\times19}+\frac{1}{19\times20}\right)\)

             \(=\frac{1}{2}\times\left(\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{2\times3}+...+\frac{1}{19\times20}\right)\)

               \(=\frac{1}{2}\times\left(\frac{1}{1\times2}-\frac{1}{19\times20}\right)\)

                \(=\frac{1}{2}\times\frac{189}{380}\)

                  \(=\frac{189}{760}\)

ĐÃ ĐÁP ỨNG THỈNH CẦU

😃😃😃

a )  \(-\frac{3}{7}.\frac{3}{11}+-\frac{3}{7}.\frac{8}{11}+1\frac{3}{7}\)

\(=-\frac{3}{7}.\left(\frac{3}{11}+\frac{8}{11}\right)+\frac{10}{7}\)

\(=-\frac{3}{7}.\frac{11}{11}+\frac{10}{7}\)

\(=-\frac{3}{7}.1+\frac{10}{7}\)

\(=\frac{10}{7}\)

b )   \(75\%.10,5=\frac{3}{4}.10,5=7,875\)

c )  \(5-3.\left(\left|-4\right|-30:15\right)\)

\(=5-3.\left(4-2\right)\)

\(=5-3.2\)

\(=5-6\)

\(=-1\)

d )  \(-\frac{5}{7}.\frac{2}{11}+-\frac{5}{7}.\frac{9}{11}+1\frac{5}{7}\)

\(=-\frac{5}{7}.\left(\frac{2}{11}+\frac{9}{11}\right)+\frac{12}{7}\)

\(=-\frac{5}{7}.1+\frac{12}{7}\)

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

\(=1\)

Chúc bạn học tốt !!! 

\(\Leftrightarrow-\dfrac{2}{5}\left(4x-3\right)^2=-\dfrac{5}{18}\)

\(\Leftrightarrow\left(4x-3\right)^2=\dfrac{25}{36}\)

\(\Leftrightarrow4x-3\in\left\{\dfrac{5}{6};-\dfrac{5}{6}\right\}\)

hay \(x\in\left\{\dfrac{23}{24};\dfrac{13}{24}\right\}\)