b.

\(=x^2+2xy+y^2-2xy-2xy=\left(x+y\right)^2-4xy=7^2-4.6=49-24=25\)

`(-13 .2/5 +( -2/9) : 5/2 + 2/5 . 11/9) . 5/2`

`=(-13 . 2/5 - 2/9 . 2/5 + 2/5 . 11/9).5/2`

`=[ 2/5 . ( -13 - 2/9 + 11/9).5/2`

`=[2/5. (-12)] . 5/2`

`=(-24)/5 . 5/2`

`= (-24.5)/(5.2)`

`=-120/10`

`=-12`

\(\left(-13.\dfrac{2}{5}+-\dfrac{2}{9}:\dfrac{5}{2}+\dfrac{2}{5}.\dfrac{11}{9}\right).\dfrac{5}{2}\)

\(=\left[\dfrac{2}{5}\left(-13-\dfrac{2}{9}+\dfrac{11}{9}\right)\right]\dfrac{5}{2}\)

\(=\dfrac{2}{5}.-12.\dfrac{5}{2}=-12\)

$#flo2k9$

_________________________________________

`(-13 . 2/5 + -2/9 : 5/2 + 2/5 . 11/9) . 5/2`

`= (-13 . 2/5  + -2/9 . 2/5 + 2/5 . 11/9) . 5/2`

`= [(-13 + -2/9 + 11/9) . 2/5) . 5/2`

`= (-12) . 2/5 . 5/2`

`= -12 . 1`

`= -12`

bài trên thấy làm ròi
You always go to bed at 9 o'clock
We usually go to the cinema on Wednesday
I often read a magazine on Sunday morning
She never eats fish
He always does his homework on Fridays

2. You always go to bed at 6 o'clock.
3. We usually go to the cinema on Wed.
4. I often read a magazine on Sun morning.
5. She never eats fish.
6. He always does his HW on Fri.
tên ngày mik ziết tắt nha :))

a: \(=7^8\)

b: \(=3^{16}\)

c: \(=\left(-6\right)^6=6^6\)

d: \(=\left(-2\right)^{11}\)

e: \(=\left(-0.1\right)^5\)

f: \(=\left(\dfrac{4}{5}\right)^7\)

`7^3*7^5=7^{3+5}=7^8`

`3^7*3^9=3^{7+9}=3^16`

`(-6)^5*(-6)=(-6)^6`

`(-2)^5*(-2)^6=(-2)^{5+6}=(-2)^{11}`

`(-0,1)^2*(-0,1)^3=(-0,1)^{2+3}=(-0,1)^6`

Các câu còn lại tương tự nhé

7^3.7^5 = 7^8

3^7.3^9 = 3^16

(-6)^5.(-6) = (-6)^6

(-2)^5.(-2)^6 = (-2)^11

(-0,1)^2.(-0,1)^3 = (-0,1)^5

(4/5)^4.(4/5)^3 = (4/5)^7

(1/2).(1/2)^2 = (1/2)^3

(-1/2).(-1/2)^3 = (-1/2)^4

(-3/2)^3.(-3/2)^2 = (-3/2)^5

(-2).2^8 ( câu này thì tui ko nhớ, sorry )

a: A=-2/5+2/5+3/4-3/4+6/7=6/7

b: A=-1/8-7/8+7/9+6/7+1/7

=7/9

c: A=2/3+2/7=20/21

e: \(=\dfrac{4\cdot13-4\cdot40}{3\cdot9}=\dfrac{4\cdot\left(-27\right)}{-27}=-4\)

`A = -2/5 + 3/(-4) + 6/7 + 3/4 + 2/5`

`A=  (-2/5+2/5)+(3/(-4) + 3/4) + 6/7`

`A = 0+0+6/7`

`A=6/7`

________________________

`B=-1/8 + 7/9 + 7/(-8) + 6/7 + 2/14`

`B = (-1/8 + 7/(-8)) + (6/7 + 2/14) + 7/9`

`B = -1 + 1 + 7/9`

`B = 0+ 7/9`

`B  =7/9`

_________________________________________

`A = 2/3 + 1/5 . 10/7`

`A = 2/3 + (1xx10)/(5xx7)`

`A = 2/3 + 57/35`

`A= 241/105`

___________________________

`B = 7/12 - 27/7 . 1/18`

`B = 7/12 - (27.1)/(7.18)`

`B=7/12- 3/14`

`B= 31/84`

__________________________

`4/9 . 13/3 - 4/3 . 40/9`

`=(4.13)/(9.3) - (4.40)/(3.9)`

`=(4.13-4.40)/(9.3)`

`=(4.(13-40))/27`

`=(4.(-27))/27`

`=-4`

____________________________________

`M=1/(3.5) + 1/(5.7) + 1/(7.9) + .... +1/(97.99)`

`M = 1/2 . (2/(3.5) + 2/(5.7) + 2/(7.9) + .... +2/(97.99))`

`M = 1/2 . (1/3 - 1/5 + 1/5 - 1/7 + ...... + 1/97 - 1/99)`

`M = 1/2 . (1/3 - 1/99)`

`M = 1/2 . 32/99`

`M= 16/99`

a/\(A=\left(-\dfrac{2}{5}+\dfrac{2}{5}\right)+\left(\dfrac{3}{-4}+\dfrac{3}{4}\right)+\dfrac{6}{7}=0+0+\dfrac{6}{7}=\dfrac{6}{7}\)

b/ \(B=\left(\dfrac{-1}{8}+\dfrac{7}{-8}\right)+\dfrac{7}{9}+\left(\dfrac{6}{7}+\dfrac{2}{14}\right)=\left(-\dfrac{1}{8}+\dfrac{-7}{8}\right)+\dfrac{7}{9}+\left(\dfrac{6}{7}+\dfrac{1}{7}\right)\\ =-1+\dfrac{7}{9}+1=0+\dfrac{7}{9}=\dfrac{7}{9}\)

c/

\(A=\dfrac{2}{3}+\dfrac{1.10}{5.7}=\dfrac{2}{3}+\dfrac{1.5.2}{5.7}=\dfrac{2}{3}+\dfrac{2}{7}=\dfrac{20}{21}\)

D/

\(B=\dfrac{7}{12}-\dfrac{27.1}{7.18}=\dfrac{7}{12}-\dfrac{9.3.1}{7.2.9}=\dfrac{7}{12}-\dfrac{3}{14}=\dfrac{31}{84}\)

E/

\(=\dfrac{4}{9}.\dfrac{13}{3}-\dfrac{4}{9}.\dfrac{40}{3}=\dfrac{4}{9}.\left(\dfrac{13}{3}-\dfrac{40}{3}\right)=\dfrac{4}{9}.\left(-\dfrac{27}{3}\right)=\dfrac{4}{9}.\left(-9\right)=-4\)

F/

\(\Rightarrow2M=2\left(\dfrac{1}{3.5}+\dfrac{1}{5.7}+...+\dfrac{1}{97.99}\right)\)

\(2M=\dfrac{2}{3.5}+\dfrac{2}{5.7}+...+\dfrac{2}{97.99}\)

\(2M=\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{97}-\dfrac{1}{99}\\ 2M=\dfrac{1}{3}-\dfrac{1}{99}=\dfrac{32}{99}\)

\(\Rightarrow M=\dfrac{32}{99}:2=\dfrac{16}{99}\)

Áp dụng đl pytago đảo vào tg ABC

Ta thấy : \(BC=\sqrt{AB^2+AC^2}\)

\(50=\sqrt{48^2+14^2}\)

=> tg ABC vuông tại A

=> góc B + góc C = 90^o ( phụ nhau )

=> \(sinB=cosC\)

=> góc C = 60^o

=> phgiác góc C = 30^o

Solar energy will be used by many countries in the world

How will you travel from one place to another

We will reduce the use of electricity to save our energy

There are always traffic jams during rush-hours

1 Solar enery will be used by many countries in the world

2 How will you travel from one place to another

3 We will reduce the use of electricity to save our energy

4 There are always traffic jam during rush-hours

1. Solar enery will be used by many countries in the world.

2. How will you travel from one place to another.

3. We will reduce the use of electricity to save our energy.

4. There are always traffic jam during rush-hours.