leminhduc làm gì mk chả hiểu lớp 6 làm gì có căn rồi 

\(1+3+5+......+x=2500\)

\(\Rightarrow\left[\left(x-1\right):2+1\right].\left(x+1\right):2=2500\)

\(\Rightarrow\left(\frac{x}{2}-\frac{1}{2}+1\right).\left(x+1\right)=2500.2\)

\(\Rightarrow\left(\frac{x}{2}+\frac{1}{2}\right).\left(x+1\right)=5000\)

\(\Rightarrow\frac{x^2}{2}+\frac{1}{2}x+\frac{x}{2}+\frac{3}{2}=5000\)

\(\Rightarrow\frac{x^2+x+x+3}{2}=5000\)

\(\Rightarrow x^2+2x+3=5000.2\)

\(\Rightarrow x^2+2x.1+1^2+3-1^2=10000\)

\(\Rightarrow\left(x+1\right)^2+2=10000\)

\(\Rightarrow\left(x+1\right)^2=10000-2\)

\(\Rightarrow\left(x+1\right)^2=9998\)

\(\Rightarrow x+1=\sqrt{9998}\)

\(\Rightarrow x=\sqrt{9998}-1\)

x=99,985

1, Ta có :

     \(x+\frac{3}{5}=\frac{4}{7}\div\frac{8}{21}\)

    \(x+\frac{3}{5}=\frac{4}{7}\times\frac{21}{8}\)

    \(x+\frac{3}{5}=\frac{3}{2}\)

    \(x=\frac{3}{2}-\frac{3}{5}\)

    \(x=\frac{15}{10}-\frac{6}{10}\)

    \(x=\frac{9}{10}\)

Vậy x = \(\frac{9}{10}\)

2, Ta có :

    \(\frac{2}{3}+\frac{3}{4}\div x=-\frac{1}{6}\)

    \(\frac{3}{4}\div x=-\frac{1}{6}-\frac{2}{3}\)

    \(\frac{3}{4}\div x=-\frac{1}{6}-\frac{4}{6}\)

    \(\frac{3}{4}\div x=-\frac{5}{6}\)

    \(x=\frac{3}{4}\div\left(-\frac{5}{6}\right)\)

    \(x=\frac{3}{4}\times\left(-\frac{6}{5}\right)\)

    \(x=-\frac{9}{10}\)

Vậy x = \(-\frac{9}{10}\)

thanks bạn nha

a) ( 1/2-1/3-1/6).(1/2+2/3+3/4+...+2017/2018) + 3/4.x = 9/10

0.(1/2+2/3+3/4+...+2017/2018) + 3/4.x = 9/10

0+3/4.x = 9/10

3/4.x = 9/10

x = 9/10: 3/4

x = 6/5

b) x + ( 3/1.3+3/3.5+...+3/13.15) = 11/5

x + 3/2. ( 1-1/3 + 1/3 - 1/5 + ...+ 1/13 - 1/15) = 11/5

x + 3/2. ( 1-1/15) = 11/5

x + 3/2.14/15 = 11/5

x + 7/5 = 11/5

x = 11/5 - 7/5

x = 4/5

..... là gì?

a) ( 1/2-1/3-1/6).(1/2+2/3+3/4+...+2017/2018) + 3/4.x = 9/10

0.(1/2+2/3+3/4+...+2017/2018) + 3/4.x = 9/10

0+3/4.x = 9/10

3/4.x = 9/10

x = 9/10: 3/4

x = 6/5

b) x + ( 3/1.3+3/3.5+...+3/13.15) = 11/5

x + 3/2. ( 1-1/3 + 1/3 - 1/5 + ...+ 1/13 - 1/15) = 11/5

x + 3/2. ( 1-1/15) = 11/5

x + 3/2.14/15 = 11/5

x + 7/5 = 11/5

x = 11/5 - 7/5

x = 4/5

Đề hơi khó hiểu bn nhé

\(\left(\dfrac{1}{4}x-\dfrac{1}{8}\right).\dfrac{3}{4}=\dfrac{1}{4}\)

\(\dfrac{1}{4}x-\dfrac{1}{8}=\dfrac{1}{4}:\dfrac{3}{4}=\dfrac{1}{3}\)

\(\dfrac{1}{4}x=\dfrac{1}{3}+\dfrac{1}{8}=\dfrac{11}{24}\)

\(x=\dfrac{11}{24}:\dfrac{1}{4}=\dfrac{11}{6}\)

\(\left(\dfrac{1}{4}x\times\dfrac{-1}{8}\right)\times\dfrac{3}{4}=\dfrac{1}{4}< =>\dfrac{-x}{32}\times\dfrac{3}{4}=\dfrac{1}{4}< =>\dfrac{-x}{32}=\dfrac{1}{4}:\dfrac{3}{4}< =>\dfrac{-x}{32}=\dfrac{1}{3}< =>x=\dfrac{1}{3}\times\left(-32\right)< =>x=\dfrac{-32}{3}\)

5A=5²+5³+...+5²⁰¹⁸

5A-A=5²⁰¹⁸-5

4A=5²⁰¹⁸-5

4A+5=5²⁰¹⁸-5=5

4A+5=5²⁰¹⁸

Ta có: \(A=5+5^2+5^3+...+5^{2017}\)

          \(5A=5^2+5^3+5^4+...+5^{2018}\)

\(5A-A=5^{2018}-5\)

Hay \(4A=5^{2018}-5\)

\(\Rightarrow4A+5=5^x\)

\(\Rightarrow\left(5^{2018}-5\right)+5=5^x\)

\(\Rightarrow5^{2018}=5^x\)

\(\Rightarrow x=2018\)

Học tốt nha!!!