a: =>x-22=9

hay x=31

=x(95-35-55+225)=230x

= 230x nha bn

230x

Ai nhanh nhất k nhiều nhất nhé

Bài này đề bài là tìm x

S=1+4+7+..+n

Tổng S có số số hạng là \(\frac{\left(n-1\right)}{3}+1=\frac{n+2}{3}\)

Tổng S có giá trị là

\(S=\frac{\left(n+1\right)}{2}.\frac{n+2}{3}=\frac{\left(n+1\right)\left(n+2\right)}{6}\)

1/ a/\(-\frac{7}{18}=\left(-\frac{7}{2}\right)\left(\frac{1}{9}\right)\)

b/\(-\frac{7}{18}=\left(-\frac{7}{9}\right):2\)

2/

a/\(\frac{7}{15}\cdot\left(-\frac{3}{8}-\frac{3}{7}\right)=\frac{7}{15}\cdot\left(-\frac{45}{56}\right)=-\frac{3}{8}\)

b/\(\left(-\frac{3}{4}+\frac{2}{5}\right):\frac{3}{7}+\left(\frac{3}{5}+-\frac{4}{4}\right):\frac{3}{7}\)

\(=\left(-\frac{7}{20}\right):\frac{3}{7}+\left(-\frac{2}{5}\right):\frac{3}{7}\)

\(=\left(-\frac{49}{60}\right)+\left(-\frac{14}{15}\right)=-\frac{7}{4}\)

c/\(\frac{2}{3}\cdot\left(-\frac{5}{2}\right)+\frac{10}{15}\cdot\left(-\frac{3}{7}\right)-\frac{2}{3}\cdot\left(-\frac{5}{3}\right)\)

\(=\frac{2}{3}\cdot\left(-\frac{5}{2}-\frac{3}{7}+\frac{5}{3}\right)=-\frac{53}{63}\)

3/

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

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

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

4/ 

a/ Ta có 2 trường hợp:

TH1: \(x-3,5=7,5\)

\(x=7,5+3,5=11\)

TH2: \(x-3,5=-7,5\)

\(x=-7,5+3,5=-4\)

b/ Ta có 2 trường hợp:

TH1:\(x-0,4=3,6\)

\(x=4\)

TH2: \(x-0,4=-3,6\)

\(x=-3.2\)

c/ Ta có 2 trường hợp:

TH1:\(x+\frac{4}{5}=\frac{3}{2}\)

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

TH2:\(x+\frac{4}{5}=-\frac{3}{2}\)

\(x=-\frac{32}{10}\)

1) \(\frac{2}{5}\div\frac{3}{5}\times x+\frac{4}{7}=\frac{1}{3}+\frac{4}{7}\)

     \(\frac{2}{5}\times\frac{5}{3}\times x+\frac{4}{7}=\frac{19}{21}\)

       \(\frac{2}{3}\times x+\frac{4}{7}=\frac{19}{21}\)

      \(\frac{2}{3}\times x=\frac{19}{21}-\frac{4}{7}\)

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

         \(\Rightarrow x=\frac{1}{3}\div\frac{2}{3}\)

          \(\Rightarrow x=\frac{1}{3}\times\frac{3}{2}\)

           \(\Rightarrow x=\frac{1}{2}\)