(x-1)/3=8/6?????

1 / 5 + x = 3 / 7 + 1 / 3

1 / 5 + x = 16 /21

x            = 16 / 21 - 1 / 5

x            = 59 / 105

x - 1 / 2 = 2 / 3 - 1 / 5

x - 1 / 2 = 7 / 15

         x  = 7 / 15 + 1 / 2

         x  = 29 / 30

3 / 5 * x = 2 / 7+ 1 / 4

3 / 5 * x = 15 / 28

          x = 15 / 28 : 3 / 5

          x = 25 / 28

7 / 8 : x = 1 / 6 * 2 / 3

7 / 8 : x = 1 / 9

          x = 7 / 8 : 1 / 9

          x = 63 / 8

A) Ta có: \(\frac{\left(x+1\right)x}{2}=16290\)

=> \(\left(x+1\right)x=32580\)

Sau đó tự tìm

b) \(7^{x+3}+7^{x+5}=17150\)

\(7^{2x+8}=17150\)

Tự tính tiếp nhé

- 12.[ x - 5 ] + 7.[ 3 - x ] = 5

=> - 12x + 60 + 21 - 7x = 5

=> ( - 12x - 7x ) + 60 + 21 = 5

=> - 19x + 81 = 5

=> - 19x = 5 - 81

=> - 19x = - 76

=> x = ( - 76 ) : ( - 19 )

=> x = 4

Vậy x = 4

-12(x-5)+7(3-x)=5

<=>(-12x)-(-60)+21-7x=5

<=>(-12x)+60+21-7x=5

<=>(-12x-7x)+81=5

<=>(-19x)=5-81=-76

<=>x=(-76):(-19)

<=>x=4

VẬy x=4

sẽ bằng: -12.x-(-12).5+7.3-7.x=5

= -12x+60+21-7x=5

Áp dụng quy tắc chuyển vế ta sẽ có

-12x-7x= 5-60-21= -76

-19x= -76 => x= -76/-19=4

\(\left(\frac{3}{5}.x-\frac{2}{3}.x-x\right).\frac{1}{7}=\frac{-5}{21}\)

\(\Rightarrow x.\left(\frac{3}{5}-\frac{2}{3}-1\right).\frac{1}{7}=\frac{-5}{21}\)

Tính trong ngoặc trước rồi qui ra <=> Tính nốt đi !!!

Tính nốt cho ๖ۣۜҨž乡тяầи♚νăи♚нùиɢ❦

\(\left(\frac{3}{5}-\frac{2}{3}-1\right)x.\frac{1}{7}=-\frac{5}{21}\)

\(\Rightarrow x.\frac{-16}{15}=-\frac{5}{21}:\frac{1}{7}\)

\(\Rightarrow x.-\frac{16}{15}=-\frac{5}{3}\)

\(\Rightarrow x=-\frac{5}{3}:-\frac{16}{15}\)

\(\Rightarrow x=\frac{25}{16}\)

\(\frac{2}{3}:\frac{x}{5}+\frac{5}{7}=\frac{2}{7}:\frac{3}{5}+\frac{9}{10}\)

\(\frac{2}{3}.\frac{5}{x}=\frac{2}{7}.\frac{5}{3}+\frac{9}{10}-\frac{5}{7}\)

\(\frac{10}{3}:x=\frac{10}{21}+\frac{9}{10}-\frac{5}{7}=\frac{100+189-150}{210}=\frac{139}{210}\)

\(x=\frac{700}{139}\)

\(\Leftrightarrow\dfrac{7^x.7^2+7^x.7+7^x}{57}=\dfrac{5^{2x}+5^{2x}.5+5^{2x}.5^3}{131}\)

\(\Leftrightarrow7^x\left(\dfrac{7^2+7+1}{57}\right)=5^{2x}\left(\dfrac{1+5+5^3}{131}\right)\)

\(\Leftrightarrow7^x\dfrac{57}{57}=5^{2x}\dfrac{131}{131}\Leftrightarrow7^x=5^{2x}\Leftrightarrow7^x=25^x\Leftrightarrow x=0\)

0

x=0