\(1+3+5+...+2007+2009+2011\)

\(=\left(2011+1\right).\left[\left(2011-1\right)\div2+1\right]\div2\)

\(=2012.1006\div2\)

\(=1012036\)

mình cảm ơn

2×(x-1)²=4

2×(x-1)²=2²

2×(x-1)=2

x-1=2:2

x-1=1

x=1+1

x=2

 Vậy x = 2

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

\(\Leftrightarrow\left[{}\begin{matrix}x=\sqrt{2}+1\\x=-\sqrt{2}+1\end{matrix}\right.\)

a) \(\dfrac{5}{5}\) và \(\dfrac{4}{5}\)

b) \(\dfrac{5}{9}\) và \(\dfrac{18}{9}\)

c) \(\dfrac{15}{5}\) và \(\dfrac{9}{5}\)

d) \(\dfrac{16}{4}\) và \(\dfrac{3}{4}\)

a: 1=5/5

4/5=4/5

b: 5/9=5/9

2=18/9

c: 3=15/5

9/5=9/5

d: 4=16/4

3/4=3/4

3 + 4 + 5 + ... + x = 525

=> 1 + 2 + 3 + 4 + 5 + ... + x = 1 + 2 + 525

=> (1 + x) × x : 2 = 528

=> (1 + x) × x = 528 × 2

=> (1 + x) × x = 1056 = 33 × 32

=> x = 32

ta có : số số hạng là :

\(\left(x-3\right):1+1=x-2\) ( số số hạng )

tổng là : \(\left(x+3\right).\left(x-2\right):2=525\)

               \(\left(x+3\right).\left(x-2\right)=1050\)

Mà 30 x 35 = 1050

\(\Rightarrow x=32\)

a: \(x+\dfrac{3}{9}=\dfrac{7}{6}\cdot\dfrac{2}{3}\)

=>\(x+\dfrac{1}{3}=\dfrac{14}{18}=\dfrac{7}{9}\)

=>\(x=\dfrac{7}{9}-\dfrac{1}{3}=\dfrac{7}{9}-\dfrac{3}{9}=\dfrac{4}{9}\)

b: \(x-\dfrac{2}{3}=\dfrac{1}{8}:\dfrac{5}{4}\)

=>\(x-\dfrac{2}{3}=\dfrac{1}{8}\cdot\dfrac{4}{5}=\dfrac{1}{10}\)

=>\(x=\dfrac{1}{10}+\dfrac{2}{3}=\dfrac{3+20}{30}=\dfrac{23}{30}\)

TThế giới oi oi oi 

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