a) x + 3/5 = -1/15

=> x = -1/15 - 3/5

=> x = -2/3

b) x/14 = 1/7 - 3/14

=> x/14 = -1/14

=> x = -1

c) -1/2x + 1/5 = 3/10

=> -1/2x = 3/10 - 1/5

=> -1/2x = 1/5

=> x = 1/5 : (-1/2)

=> x = -2/5

d) 4/5 - (2/15 + x) = 1/15

=> 4/5 - 2/15 - x = 1/15

=> 2/3 - x = 1/15

=> x = 2/3 - 1/15

=> x = 3/5

4/7 . x - 2/5 = 1/5

=> 4/7.x = 1/5 + 2/5

=> 4/7.x = 3/5

=> x = 3/5 : 4/7

=> x = 21/20

3/4 . x = 1

=> x = 1 : 3/4

=> x = 1 . 4/3

=> x = 4/3

Vậy x = 4/3

theo đề 

suy ra hsk+hs tb=100%-25%=75% so với cả lớp

Số học sinh cả lớp là :

     10 : 25% = 40 ( học sinh )

Tổng số học sinh khá và trung bình là :

    40 - 10 = 30 ( học sinh )

Tỉ số % giữa học sinh khá và trung bình với số               học sinh cả lớp : 

                  30 . 100 / 40 (%) = 75 %

              Vậy....

                        #Louis

đề bài có bị thiếu vậy không bạn :))

ko nha bn, giải đc ko zậy ạ, nếu ko đc cx ko sao nha

\(\frac{x-1}{6}=\frac{6}{x-1}\)

\(\Rightarrow\left(x-1\right)^2=36\)

\(\Rightarrow\orbr{\begin{cases}x-1=6\\x-1=-6\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=7\\x=-5\end{cases}}\)

a) \(\frac{x-1}{6}=\frac{6}{x-1}\)

<=> (x - 1)(x - 1) = 6.6

<=> (x - 1)² = 36

<=> (x - 1)² = 6²

\(\Leftrightarrow\orbr{\begin{cases}x-1=6\\x-1=-6\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=7\\x=-5\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=7\\x=-5\end{cases}}\)

b) \(\frac{\left|x+3\right|}{5}=\frac{1}{4}\)

\(\Leftrightarrow\frac{5.\left|x+3\right|}{5}=\frac{5.1}{4}\)

\(\Leftrightarrow\left|x+3\right|=\frac{5}{4}\)

\(\Leftrightarrow\orbr{\begin{cases}x+3=\frac{5}{4}\\x+3=-\frac{5}{4}\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=-\frac{7}{4}\\x=-\frac{17}{4}\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=-\frac{7}{4}\\x=-\frac{17}{4}\end{cases}}\)

Nowadays, a variety of environmental problems affect our entire world. As globalization continues and Earth’s natural processes, few societies are being left untouched by major environmental troubles.

First of all, some of the largest problems now affecting to the world, air pollution and hazardous waste. These issues can be avoided with the recycling, for example in order to reduce pollution, we can minimize the energy spends on industrial production. Consequently, the greenhouse emission can be reduced which are harmful for the environment and our health. Furthermore, most of the landfill sides are filled up with a lot of waste products that could have been recycled, especially waste materials that belong to non-biodegradable category which takes a long time to discompose. In this way, recycling enable proper usage of these waste products and saves space for landfill.

Plant more trees. This is easy, you know? Choose an open area/ground near your residence or workplace. Plant a tree every month, encourage your friends and colleagues to join you. Have more and more trees planted and there will come a day when you have a green stretch of land thanks to your effort.

Walk more, drive less. Now that's not very difficult, is it? Choose to walk short distances instead of taking your car every time. Walking to the gym, to work (if it's not very far), go walking to run errands. Or use a bicycle. Both cycling and walking are good exercises. And each time you avoid using your car, you are contributing to reducing air pollution. You are saving fuel, saving money and getting a good workout too.

Nowadays, a variety of environmental problems affect our entire world. As globalization continues and Earth’s natural processes, few societies are being left untouched by major environmental troubles.

First of all, some of the largest problems now affecting to the world, air pollution and hazardous waste. These issues can be avoided with the recycling, for example in order to reduce pollution, we can minimize the energy spends on industrial production. Consequently, the greenhouse emission can be reduced which are harmful for the environment and our health. Furthermore, most of the landfill sides are filled up with a lot of waste products that could have been recycled, especially waste materials that belong to non-biodegradable category which takes a long time to discompose. In this way, recycling enable proper usage of these waste products and saves space for landfill.

Plant more trees. This is easy, you know? Choose an open area/ground near your residence or workplace. Plant a tree every month, encourage your friends and colleagues to join you. Have more and more trees planted and there will come a day when you have a green stretch of land thanks to your effort.

Walk more, drive less. Now that's not very difficult, is it? Choose to walk short distances instead of taking your car every time. Walking to the gym, to work (if it's not very far), go walking to run errands. Or use a bicycle. Both cycling and walking are good exercises. And each time you avoid using your car, you are contributing to reducing air pollution. You are saving fuel, saving money and getting a good workout too.

\(\frac{a}{b}=\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+...+\frac{1}{9}+\frac{1}{10}\)

\(=\left(\frac{1}{3}+\frac{1}{10}\right)+\left(\frac{1}{4}+\frac{1}{9}\right)+\left(\frac{1}{5}+\frac{1}{8}\right)+\left(\frac{1}{6}+\frac{1}{7}\right)\)

\(=\frac{13}{30}+\frac{13}{36}+\frac{13}{40}+\frac{13}{42}=\frac{13.\left(84+70+63+60\right)}{2520}=\frac{13.277}{2520}\)

Phân số \(\frac{13.277}{2520}\) tối giản nên \(a=13m\) \(\left(m\inℕ^∗\right)\)

Vậy \(a⋮13\)

\(\frac{4}{11}+-\frac{5}{13}-\frac{-7}{11}+-\frac{8}{13}\)

\(=\frac{4}{11}-\frac{-7}{11}+-\frac{5}{13}+-\frac{8}{13}\)

\(=1+\left(-1\right)\)

\(=0\)

- Đây là một trong những trận thuỷ chiến lớn nhất trong lịch sử chống ngoại xâm của dân tộc.

- Khẳng định nền độc lập của dân tộc, chiến thắng Bạch Đằng mở ra thời kì độc lập lâu dài của Tổ quốc.

vì >>>>>............................................................................................. chép đi