     1 phút trước

b.

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

Bình luận (1)  2 phút trước

(-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

Bình luận (3) 2 phút trước

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

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

$=\dfrac{2}{5}.-12.\dfrac{5}{2}=-12$

Bình luận (1) Vài giây trước

$#flo2k9$

_________________________________________

(-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

Bình luận (1)  6 phút trước

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

Bình luận (0) 3 phút trước

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 :))

Bình luận (0)  6 phút trước

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: $=\left(\dfrac{4}{5}\right)^7$

Bình luận (0) 3 phút trước

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

Bình luận (0) Vài giây trước

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 )

Bình luận (0)  10 phút trước

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

Bình luận (1) 5 phút trước

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

Bình luận (0) Vài giây trước

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/

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

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

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

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

Bình luận (0)  8 phút trước

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 = 90o ( phụ nhau )

=> $sinB=cosC$

=> góc C = 60o

=> phgiác góc C = 30o

Bình luận (0)  13 phút trước

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

Bình luận (0) 13 phút trước

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

Bình luận (0) 2 phút trước

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.

Bình luận (0)