4/7;-3/4;1/-5

tính máy tính đấy cậu ơi ?

1, Tính tổng:

\(C=\frac{5}{7}\cdot\frac{5}{11}+\frac{5}{7}\cdot\frac{2}{11}-\frac{5}{7}\cdot\frac{14}{11}\)

\(=\frac{5}{7}\cdot\left(\frac{5}{11}+\frac{2}{11}-\frac{14}{11}\right)=\frac{5}{7}\cdot\frac{-7}{11}=\frac{-5}{11}\)

2, Tìm x:

\(x+\frac{5}{5\cdot9}+\frac{4}{9\cdot13}+\frac{4}{13\cdot17}+...+\frac{4}{41\cdot45}=\frac{-37}{45}\)

\(\Rightarrow x+\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+\frac{1}{13}-\frac{1}{17}+...+\frac{1}{41}-\frac{1}{45}=\frac{-37}{45}\)

\(\Rightarrow x+\frac{1}{5}-\frac{1}{45}=\frac{-37}{45}\Rightarrow x+\frac{9}{45}-\frac{1}{45}=\frac{-37}{45}\)

\(\Rightarrow x+\frac{8}{45}=\frac{-37}{45}\Rightarrow x=\frac{-37}{45}-\frac{8}{45}=\frac{-45}{45}=-1\)

- Các bài tìm x còn lại bạn cứ theo trình tự thực hiện phép tính mà làm nhé!

\(C=\frac{5}{7}\cdot\frac{5}{11}+\frac{5}{7}\cdot\frac{2}{11}-\frac{5}{7}\cdot\frac{14}{11}\)

\(=\frac{5}{7}\cdot\left(\frac{5}{11}+\frac{2}{11}-\frac{14}{11}\right)\)

\(=\frac{5}{7}\cdot-\frac{7}{11}\)

\(=-\frac{5}{11}\)

1. Pack your lunch in a lunch box instead of a plas bag.

2. Use your own bag when you go shopping. 

3. Turn off the lights when you don't use them.

4. Donate your old clothes or swap them with your friends.

5. Turn off the tap when you are brushing your teeth. 

\(|x|< 2013\)

\(\Rightarrow x=\pm2013;\pm2012;...\pm1\)

Tổng của chúng bằng: \(\left(-2013+2013\right)+\left(-2012+2012\right)+...+\left(-1+1\right)\)

Mỗi cặp trên có tổng đều bằng 0

\(\Rightarrow\)Tổng đó bằng 0

~Học tốt~

vì /x/<2013

Mà x thuộc z

Nên ta có x thuộc ( 2012;2011;…;-2012)

Ta có tổng giá trị các số nguyên x thỏa mãn là

2012+2011+2010+…+(-2011)+(-2012)

(2012+-2012)+(2011+-2011)+…+(1+-1)

=0

k cho mình

1. If/you/burn rubbish/you/produce harmful smoke

-> If you burn rubbish, you will produce harmful smoke 

2.If/we/reuse bottles/we/save a lot of money

-> If we reuse bottles, we will save a lot of money 

3. If/students/use recycled paper/they/save/trees

-> if students use recycled paper, they will save the trees

4. If/students/plant trees in the schoolyard/their school/greener place

-> if students plant trees in the school yard, their school will be a greener place

1. If/you/burn rubbish/you/produce harmful smoke

-> If you burn rubbish, you will produce harmful smoke 

2.If/we/reuse bottles/we/save a lot of money

-> If we reuse bottles, we will save a lot of money 

3. If/students/use recycled paper/they/save/trees

-> if students use recycled paper, they will save the trees

4. If/students/plant trees in the schoolyard/their school/greener place

-> if students plant trees in the school yard, their school will be a greener place