1) \(x+\dfrac{30}{100}x=-1,31\)

\(\Leftrightarrow x+\dfrac{3}{10}x=-\dfrac{131}{100}\)

\(\Leftrightarrow100x+30x=-131\)

\(\Leftrightarrow130x=-131\)

\(\Leftrightarrow x=-\dfrac{131}{130}\)

Vậy \(x=-\dfrac{131}{130}\)

b) \(\left(4,5-2x\right)\cdot\left(-1\dfrac{4}{7}\right)=\dfrac{11}{4}\)

\(\Leftrightarrow\left(\dfrac{9}{2}-2x\right)\cdot\left(-\dfrac{4}{7}\right)=\dfrac{11}{4}\)

\(\Leftrightarrow-\dfrac{18}{7}+\dfrac{8}{7}x=\dfrac{11}{4}\)

\(\Leftrightarrow-72+32x=77\)

\(\Leftrightarrow32x=77+72\)

\(\Leftrightarrow32x=149\)

\(\Leftrightarrow x=\dfrac{149}{32}\)

Vậy \(x=\dfrac{149}{32}\)

\(A=1+2+3+4+5+....+99+100\)

\(A=100(100+1):2=5050\)

\(B=\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+.....+\dfrac{1}{9900}\)

\(B=\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+.....+\dfrac{1}{99.100}\)

\(B=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+....+\dfrac{1}{99}-\dfrac{1}{100}\)

\(B=1-\dfrac{1}{100}=\dfrac{99}{100}\)

x+30%x=-1,31

x+0,3=-1,31

x=-1,31-0,3

x=-1,61

Thắng Mai bảo t k cho m

x + \(\frac{3}{10}\)x - -1,31

x . ( \(1\)+ \(\frac{3}{10}\)) = -1,31

x . \(\frac{13}{10}\)= -1,31

x                = -1,31 : \(\frac{13}{10}\)

x               = \(\frac{-131}{130}\)

ai tốt bụng thì tk cho mk nha, mk đg âm điểm nè

thank you very much

\(\frac{-131}{130}\)bạn nha

CHÚC BẠN HỌC GIỎI

\(x+30\%x=-1,31\\ x+\dfrac{3}{10}x=-1\dfrac{31}{100}\\ x\cdot\left(1+\dfrac{3}{10}\right)=-\dfrac{131}{100}\\ x\cdot\dfrac{13}{10}=-\dfrac{131}{100}\\ x=-\dfrac{131}{100}:\dfrac{13}{10}=\dfrac{-131}{100}\cdot\dfrac{10}{13}=-\dfrac{131}{130}\)

x + 30%x = - 1,31

1,3 x = - 1,31

x = -131/130

131/130

k nha

       x + 30% x = -1,31

<=> x + 3/10 x = -32/31

<=>1x + 3/10 x=-32/31

<=> 10/10 x + 3/10 x = -32/31

<=> x . 13/10 = -32/31

=> x= -32/31 : 13/10=.....?

Ta có: x(1+30%)=-1,31

  ⇒        \(\dfrac{13}{10}\)x         =-1,31

  ⇒         x             =-1,31 : \(\dfrac{13}{10}\)

  ⇒         x             = -\(\dfrac{131}{130}\)

x + 30% x = -1,31

\(x+\dfrac{30}{100}x=-1,31\)

x+0,3x=-1,31

x.(0,3+1)=-1,31

x.1,3=-1,31

\(x=\dfrac{-1,31}{1,3}\)

\(x=-\dfrac{131}{130}\)

x+30%x=-1,31

<=> x(0.3+1)=-1,31

<=> X=\(\frac{-1,31}{1,3}\)

<=>x.(1+30%)=-1,31

<=>x.1,31=-1,31

<=>x=-1

\(x+30\%x=-1,31\)

\(\Leftrightarrow x+\dfrac{30}{100}x=-1,31\)

\(\Leftrightarrow\dfrac{13}{10}x=-1,31\)

\(\Leftrightarrow x=-\dfrac{131}{130}\)

Ta có: x + 30 % x = -131/100

          x ( 1 + 30%) = -131/100

          x 13/10=-131/100

          x = -131/100 ; 13/10

          x = -131/130

 b) )x+3/-15=1/3

x = 1/3 -3/-15

x= 8/15 

=> x = \(\frac{8}{15}\)

Ta có: x + 30 % x = -131/100

          x ( 1 + 30%) = -131/100

          x 13/10=-131/100

          x = -131/100 ; 13/10

          x = -131/130

Ta có: x + 30 % x = -131/100

          x ( 1 + 30%) = -131/100

          x 13/10=-131/100

          x = -131/100 ; 13/10

          x = -131/130

\(x+\frac{3}{10}x=-\frac{131}{100}\)

\(x.\left(1+\frac{3}{10}\right)=-\frac{131}{100}\)

\(x.\frac{13}{10}=-\frac{131}{100}\)

\(x=-\frac{131}{100}:\frac{13}{10}\)

\(x=-\frac{131}{130}\)