a, 6/7 + (2/11 - 6/7) - (13/11 + 1)

= 6/7 + 2/11 - 6/7 - 13/11 - 1

= (6/7 - 6/7) - (13/11 - 2/11) - 1 

= 0 - 1 - 1

= -2

\(6,3+\left(-3,7\right)+2,4+\left(-0,3\right)=\left[6,3+2,4\right]+\left[\left(-3,7\right)+\left(-0,3\right)\right]=8,7+\left(-4\right)=8,7-4=4,7\)

\(6,3+\left(-3,7\right)+2,4+\left(-0,3\right)=\left(6,3+2,4\right)+\left[\left(-3,7\right)+\left(-0,3\right)\right]=8,7+\left(-4\right)=4,7\)

1.\(\left(\frac{-10}{15}+1\frac{1}{6}-0,5\right):\left(4\frac{4}{105}-5\frac{4}{81}\right)\)

=\(\left(\frac{-10}{15}+\frac{7}{6}-0,5\right):\left(\frac{425}{105}-\frac{409}{81}\right)\)

=\(0:\left(\frac{425}{105}-\frac{409}{81}\right)\)

=\(0\)

2. \(\frac{1}{2}\left(\frac{-11}{19}\right)-50\%.\left(\frac{-1}{19}\right)+\frac{10}{19}.\frac{1111}{2222}\)

=\(\frac{-11}{38}-\frac{-1}{38}+\frac{5}{19}\)

=\(\frac{-11}{38}+\frac{1}{38}+\frac{5}{19}\)

=\(0\)

k cho mik nha

A=7/3.4 - 9/4.5 + 11/5.6 - 13/6.7 + 15/7.8 -17/8.9+19/9.10

=(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)

=1/3-1/5+1/5-1/7+1/7-1/9+1/9+1/10

=1/3+1/10

=13/30

Vậy A = 13/30

\(A=\frac{7}{3.4}-\frac{9}{4.5}+\frac{11}{5.6}-\frac{13}{6.7}+\frac{15}{7.8}-\frac{17}{8.9}+\frac{19}{9.10}\)

\(=\frac{1}{3}+\frac{1}{4}-\frac{1}{4}-\frac{1}{5}+\frac{1}{5}+\frac{1}{6}-\frac{1}{6}-\frac{1}{7}+\frac{1}{7}+\frac{1}{8}-\frac{1}{8}-\frac{1}{9}+\frac{1}{9}+\frac{1}{10}\)=\(\frac{1}{3}+\frac{1}{10}=\frac{13}{30}\)

a)              75 - 3.(2/13+1/17-1/19)            3.[25-(2/13+1/17-1/19)]

               -------------------------------------- = ---------------------------------------------- = 3/11

                275-11.(2/13+1/17-1/19)            11.[25-(2/13+1/17-1/19)]

a)     \(\frac{75-\frac{6}{13}+\frac{3}{17}-\frac{3}{19}}{275-\frac{22}{13}+\frac{11}{17}-\frac{11}{19}}=\frac{75-3.\left(\frac{2}{13}+\frac{1}{17}-\frac{1}{19}\right)}{275-11.\left(\frac{2}{13}+\frac{1}{17}-\frac{1}{19}\right)}\)

                                                         \(=\frac{75-3}{275-11}\)

                                                         \(=\frac{72}{264}=\frac{3}{11}\)

b)          \(\frac{2}{3.5}+\frac{7}{5.12}+\frac{9}{4.39}=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{12}+\frac{3}{52}\)

                                                        \(=\frac{1}{3}-\frac{1}{12}+\frac{3}{52}\)

                                                       \(=\frac{1}{4}+\frac{3}{52}=\frac{4}{13}\)

bạn tìm 1 số để nhân cả tử cả mẫu ra để tử ra 1 so chung nha rồi tách thôi

đúng mà

Cộng 3 vào cả 2 vế và chuyển vế xong đặt nhân tử x+50 ra ngoài ta được :

(x+50)(1/39+1/37+1/35-1/33-1/31-1/29)=0

vì (1/39+1/37+1/35-1/33-1/31-1/29) khác 0

=> x+50=0

=> x=-50

Nhớ k mình nhé

Chúc bạn học  tốt

x = -50 nha