a: =-3/15+25/15=22/15

b: =-15/20-14/20=-29/20

c: =-15/8*4/5=-12/8=-3/2

d: =-30/7*1/5=-30/35=-6/7

\(3^5\)

-5+10-15+20-25+30

=(-5+10)-(15-20)-(25-30)

=5-(-5)-(-5)

=5+5+5

=5.3

=15

-5 + 10 - 15 + 20 - 25 + 30

= ( 10 + 20 + 30) - ( 5 + 15 + 25)

= 60 - 45

= 15

a)   \(\frac{x+3}{2x-1}=\frac{2}{5}\)             \(\left(x\ne\frac{1}{2}\right)\)

\(\Rightarrow\)\(5\left(x+3\right)=2\left(2x-1\right)\)

\(\Leftrightarrow\)\(5x+15=4x-2\)

\(\Leftrightarrow\)\(5x-4x=-2-15\)

\(\Leftrightarrow\)\(x=-17\)

Vậy...

= 1,035 301 587 nhé

/HT\

Ta có: \(\dfrac{1}{5}+\dfrac{4}{10}+\dfrac{9}{15}+\dfrac{16}{20}+\dfrac{25}{25}+\dfrac{36}{30}+\dfrac{49}{35}+\dfrac{64}{40}+\dfrac{81}{45}\)

\(=\dfrac{1}{5}+\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{4}{5}+\dfrac{5}{5}+\dfrac{6}{5}+\dfrac{7}{5}+\dfrac{8}{5}+\dfrac{9}{5}\)

\(=\dfrac{45}{5}=9\)

\(\dfrac{1}{5}+\dfrac{4}{10}+\dfrac{9}{15}+...+\dfrac{81}{45}\\ =\dfrac{1}{5}+\dfrac{2}{5}+\dfrac{3}{5}+...+\dfrac{9}{15}\\ =\dfrac{\left(1+2+3+...+9\right)}{15}=\dfrac{\left(1+9\right)x9:2}{15}\\ =\dfrac{10x9:2}{15}=\dfrac{45}{15}=3\)

Thanks bạn nhìu nhaaaa

5=1 chứ mấy 1=5 mà 

5=1 nha bạn

1=5;2=10;3=15;4=20;5=1

^.<

-1 = 5

2 = 10 

3=15

4 =20 

5 = -1 

Các bạn thấy đúng thì k mình nha

5=1

Câu này có người đố mình rồi .5=1.