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

\(\left(\frac{3x-2}{6}\right):\frac{1}{2}=\left(-\frac{5}{4}\right):\left(-\frac{1}{4}\right)\)

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

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

           Áp dụng công thức \(\frac{a}{b}=\frac{c}{d}\Rightarrow ad=bc\) ta đc:

                    \(\Rightarrow2\left(3x-2\right)=30\)

                    \(\Rightarrow\left(3x-2\right)=15\)

                    \(\Rightarrow3x=17\)

                         \(\Rightarrow x=\frac{17}{3}\)

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

\(\left(\frac{x}{2}-\frac{1}{3}\right):\frac{1}{2}=\left(\frac{1}{4}-\frac{6}{4}\right):1\)

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

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

\(\frac{x}{2}-\frac{1}{3}=-\frac{5}{4}\times\frac{1}{2}\)

\(\frac{x}{2}-\frac{1}{3}=-\frac{5}{8}\)

\(\frac{x}{2}=-\frac{5}{8}+\frac{1}{3}\)

\(\frac{x}{2}=-\frac{7}{24}\)

\(x\times24=-14\)

\(x=-\frac{7}{12}\)

Nhu lon

( -5 ) + 2 + / + 3/ + ( -4 ) + / -1 /

=( -5 ) +( 2 + 3)

= ( -5 ) + 5   +   [ ( -4 ) + 1 ]

=0 + (-3)

= -3

Tổng quát:

A=3+(3²+3³+3⁴+...+3ⁿ)

=> 3A=3²+3³+3⁴+3⁵+...+3ⁿ+3ⁿ⁺¹

=> 3A-A=(3²+3³+3⁴+3⁵+....+3ⁿ)+3ⁿ⁺¹-3-(3²+3³+3⁴+....+3ⁿ)=3ⁿ⁺¹-3

<=> 2A=3ⁿ⁺¹-3 => A=\(\frac{3^{n+1}-3}{2}\)(1)

Bài toán có n=10. Thay vào (1):

A=\(\frac{3^{10+1}-3}{2}=\frac{3^{11}-3}{2}\)

Áp dụng công thức \(S_n=\frac{a^{n+1}-1}{a-1}\)khi đó ta được\(s=\frac{3^{10+1}-1}{3-1}=\frac{3^{11}-1}{2}\)

mk chi lam duoc cau c thoi

suy ra 2x-1=5 hoac 2x-1=-5

          2x=6            2x=-4

          x=3                 x=-2

vay x=3 hoac x=-2

a. 3/4.x+1/3=-1/2

=>3/4.x=-1/2-1/3=-5/6

=>x=-5/6 chia 3/4=-10/9

b. -x/4=-9/x =>-x*x=4*-9

=>-2x=-36 =>x=18

c./2x-1/=5

=> 2x-1=5 =>2x=5+1=6 =>x=3

  hoặc 2x-1=-5 =>2x=-5+1=-4 =>x=-2

d,e: Sai đề rồi