\(\text{(1/15 + 1/35 + 1/63) x X = 1}\)

\(\left(\frac{2}{21}+\frac{1}{63}\right)\cdot x=1\)

\(\frac{1}{9}\cdot x=1\)

\(x=1:\frac{1}{9}\)

\(x=9.\)

Ta có: \(\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}\right).x=1\)

\(\Rightarrow\frac{1}{9}.x=1\)

\(\Rightarrow x=1:\frac{1}{9}\)

\(\Rightarrow x=9\)

Vậy x = 9

Ta có:

\(\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{63}\right).x=1\)

\(\Rightarrow\left(\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}\right).x=1\)

\(\Rightarrow\left(\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}\right).2x=2\)

\(\Rightarrow\left(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}\right).x=2\)

\(\Rightarrow\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}\right).x=2\)

\(\Rightarrow\left(\frac{1}{3}-\frac{1}{9}\right).x=2\)

\(\Rightarrow\frac{2}{9}.x=2\)

\(\Rightarrow x=2:\frac{2}{9}=9\)

Vậy x = 9

1-1/2+1/2-1/3+1/3+1/4-1/4+1/5-1/5+1/6-1/6+1/7-1/7+1/8-1/8+1/9-1/9+1/10-(1-1/3+1/3-3/5+3/5-4/7+5/9-5/9+6/11-6/11-7/13)=1+1/10-1+7/13=83/130

A = 1/15 + 1/35 + 1/63 + 1/99 + ... + 1/255

A = 1/3x5 + 1/5x7 + 1/7x9 + 1/9x11 +...+ 1/15x17

2A = 2/3x5 + 2/5x7 + 2/7x9 + .... + 1/15x17

2A = 1/3 - 1/5 + 1/5 - 1/7 + 1/7 - 1/9 + .... + 1/15 - 1/17

2A = 1/3 - 1/17 = 14/51

A = 14/51 : 2 = 7/51

ta tách biểu thức trên thành 1/ 3*5+1/ 5*7+1/ 7*9+1/ 9*11+...+1/ 15*17

từ biểu thúc trên có:

1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+...+1/15-1/17

rút gọn còn  1/3-1/17

còn lại bạn tự tính nha

\(x-\frac{2}{3}-\frac{2}{15}-\frac{2}{35}-\frac{2}{63}=30\frac{1}{9}\)

\(x=31\)

\(30\frac{1}{9}\)= \(\frac{271}{9}\)

\(x-\frac{2}{3}-\frac{2}{15}-\frac{2}{35}-\frac{2}{63}=\frac{271}{9}\)

\(x=\frac{271}{9}-\left(\frac{2}{3}+\frac{2}{15}+\frac{2}{35}+\frac{2}{63}\right)\)

\(x=\frac{263}{9}\)

~ Chúc bạn học tốt ~

X - 2/3 - 2/15 - 2/35 - 2/63 = 30 1/9

X - 2/3 - 2/15 - 2/35 - 2/63 = 271/9

X= 271/9 + 2/63 + 2/35 + 2/15+ 2/3

X = 31

( 1/15 + 1/35 + 1/63 ) * x = 1

1/9 * x = 1

x = 1 : 1/9

x = 9

Vậy x = 9

\(\left(\frac{1}{15}+\frac{1}{35}+\frac{1}{65}\right)\times x=1\)

                                  \(\frac{1}{9}\times x=1\)

                                              \(x=1:\frac{1}{9}\)

                                              \(x=1\times9\)

                                              \(x=9\)

?????????????????????????????????

a) 25/42 - 20/63 = 5/18

b) ( 9/50 - 13/75 - 1/6 ) : ( -1/2 )² = -16/25

c) ( 2/15 - 2/65 - 4/39 ) : ( 1/2 - 1/3 )² = 0

kick và kết bạn với mình nha

1/2 + 1/14 + 1/35 + 1/65 + 1/104 + 1/152 = 12/19

k

1/3 + 1/15 + 1/35 + 1/63 + 1/99 + 9999

= 1/3 + ( 1/5 + 1/35 + 1/63 ) + 1/99 = 9999

= 1/3 + 1111/9999 + 1/99

= 3333/9999 + 1111/9999 +101/9999

= 4545/9999

4546/9999

có thể giải hẳn ra được ko cái này tính máy tính cũng ra