3./x-1/=7+5

3./x-1/=12

/x-1/=12:3

/x-1/=4

TH1 : x - 1 = 4                                     TH2:X-1=-4

Đến đây em tự giải ra nhé ^^

\(3.\left|x-1\right|-5=7\)

\(\Rightarrow3\left|x-1\right|=7+5\)

\(\Rightarrow3.\left|x-1\right|=12\)

\(\Rightarrow\left|x-1\right|=12:3\)

\(\Rightarrow\left|x-1\right|=4\)

\(\Rightarrow\orbr{\begin{cases}x-1=4\\x-1=-4\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=5\\x=-3\end{cases}}\)

Vậy \(\orbr{\begin{cases}x=5\\x=-3\end{cases}}\)

de bai la gi vay

Bàn này hỏi gì vậy ? 

Bài 1:

\(A=\frac{5}{3.6}+\frac{5}{6.9}+....+\frac{5}{96.99}\)

\(\Rightarrow\frac{3}{5}A=\frac{3}{3.6}+\frac{3}{6.9}+....+\frac{3}{96.99}\)

\(\Rightarrow\frac{3}{5}A=\frac{1}{3}-\frac{1}{6}+\frac{1}{6}-\frac{1}{9}+...+\frac{1}{96}-\frac{1}{99}\)

\(=\frac{1}{3}-\frac{1}{99}=\frac{32}{99}\)

\(\Rightarrow A=\frac{32}{99}\div\frac{3}{5}=\frac{160}{297}\)

Bái 2:

\(B=\frac{2}{3.7}+\frac{2}{7.11}+...+\frac{2}{99.103}\)

\(\Rightarrow2B=\frac{4}{3.7}+\frac{4}{7.11}+....+\frac{4}{99.103}\)

\(\Rightarrow2B=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+....+\frac{1}{99}-\frac{1}{103}\)

\(=\frac{1}{3}-\frac{1}{103}=\frac{100}{309}\)

\(\Rightarrow B=\frac{100}{309}\div2=\frac{50}{309}\)

Bài 1:

Ta có:

\(\frac{5}{n.\left(n+3\right)}=\frac{5}{3}.\frac{3}{n.\left(n+3\right)}=\frac{5}{3}.\frac{\left(n+3\right)-n}{n.\left(n+3\right)}=\frac{5}{3}.\left[\frac{n+3}{n.\left(n+3\right)}-\frac{n}{n\left(n+3\right)}\right]\)\(=\frac{5}{3}\left(\frac{1}{n}-\frac{1}{n+3}\right)\)

\(\frac{5}{3.6}+\frac{5}{6.9}+\frac{5}{9.12}+...+\frac{5}{96.99}=\frac{5}{3}\left(\frac{1}{3}-\frac{1}{6}+\frac{1}{6}-\frac{1}{9}+...+\frac{1}{96}-\frac{1}{99}\right)\)

a: \(x+6\dfrac{1}{8}=8\)

=>\(x+\dfrac{49}{8}=\dfrac{64}{8}\)

=>\(x=\dfrac{64}{8}-\dfrac{49}{8}=\dfrac{15}{8}\)

b: \(\dfrac{11}{2}\cdot x=\dfrac{1}{5}:\dfrac{1}{3}\)

=>\(x\cdot\dfrac{11}{2}=\dfrac{1}{5}\cdot3=\dfrac{3}{5}\)

=>\(x=\dfrac{3}{5}:\dfrac{11}{2}=\dfrac{3}{5}\cdot\dfrac{2}{11}=\dfrac{6}{55}\)

c: \(x\cdot\dfrac{3}{5}+\dfrac{2}{5}\cdot x=\dfrac{4}{9}+\dfrac{1}{3}\)

=>\(x\left(\dfrac{3}{5}+\dfrac{2}{5}\right)=\dfrac{4}{9}+\dfrac{3}{9}\)

=>\(x\cdot1=\dfrac{7}{9}\)

=>\(x=\dfrac{7}{9}\)

a.=47-[45.16-25.12]:14]

=47-420:14

=47-30

=17

b.=50-[12:2+34]

=50-40

=10

c.=100-60:10

=100-6

=94

d.50-[(50-40);2+3]

=50-(10:2+3)

=50-8

=42

5/6+3/4 < 19/11                           4/9 x 6/5 = 8/15

17/12-9/8 < 1/3                            15/4:3/8 > 8

Ta có: \(\frac{5}{6}+\frac{3}{4}=\frac{10}{12}+\frac{9}{12}=\frac{19}{12}\)

Vì \(12>11\)

\(\Rightarrow\frac{19}{12}< \frac{19}{11}\)

\(\Rightarrow\frac{5}{6}+\frac{3}{4}< \frac{19}{11}\)

Ta có: \(\frac{17}{12}-\frac{9}{8}=\frac{34}{24}-\frac{27}{24}=\frac{7}{24}\)

Ta lại có: \(\frac{1}{3}=\frac{8}{24}\)

Vì \(8>7\)

\(\Rightarrow\frac{7}{24}< \frac{8}{24}\)

\(\Rightarrow\frac{17}{12}-\frac{9}{8}< \frac{1}{3}\)

Ta có: \(\frac{4}{9}\times\frac{6}{5}=\frac{24}{45}=\frac{8}{15}\)

Vì \(\frac{8}{15}=\frac{8}{15}\)

 \(\Rightarrow\frac{4}{9}\times\frac{6}{5}=\frac{8}{15}\)

Ta có: \(\frac{15}{4}:\frac{3}{8}=\frac{15}{4}\times\frac{8}{3}=10\)

Vì \(10>8\)

\(\Rightarrow\frac{15}{4}:\frac{3}{8}>8\)

HOK TOT

a, x=-5/33

b, x=-30

c, (Nếu dấu của bạn là giá trị tuyệt đối)      x=1/3 hoặc x=-1/3

Nếu cần mik giải rõ ràng cho

\(\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right).\left(1-\frac{1}{5}\right)\)

\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.\frac{4}{5}\)

\(=\frac{1}{3}.\frac{3}{4}.\frac{4}{5}\)

\(=\frac{1}{3}.\frac{3}{5}\)

\(=\frac{1}{5}\)

ủng hộ tớ nha

mk ko biết xin lỗi bạn nha!!!

mk ko biết xin lỗi bạn nha!!!

mk ko biết xin lỗi bạn nha!!!

mk ko biết xin lỗi bạn nha!!!