2.Sylvia always listens to music.She never watches TV

3.Chris often skates in the park.He sometimes plays computer games

4.Victoria usually goes out with friends.She never stays at home

Sylvia always listens to music. She never watches TV
Chris often skates in the park. He sometimes plays computer games
Victoria usually goes out with friends. She never stays at home

b.

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

a, \(\dfrac{2y+2x}{xy}=\dfrac{2\left(x+y\right)}{xy}=\dfrac{14}{6}=\dfrac{7}{3}\)

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

c, \(\left(x+y\right)^3-3xy\left(x+y\right)==343-3.6.7=217\)

d, \(\left\{{}\begin{matrix}y=\dfrac{6}{x}\\x+\dfrac{6}{x}=7\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{6}{x}\\x^2+6-7x=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=1;y=6\\\left[{}\begin{matrix}x=1\\x=6\end{matrix}\right.\end{matrix}\right.\)

Với x = 1 ; y = 6 thì 

\(\dfrac{1+36}{\left|1-6\right|}=\dfrac{37}{5}\)

Với x = 6 ; y = 1 thì \(\dfrac{36+1}{\left|6-1\right|}=\dfrac{37}{5}\)

mik sẽ biến đổi r bn tự thay số vào nha

a) dễ r bn tự làm nha

b)   \(x^2+y^2-2xy\)

\(=\left(x+y\right)^2-2xy-2xy=\left(x+y\right)^2-4xy\)

c)  \(x^3+y^3\)

\(=\left(x+y\right)\left(x^2-xy+y^2\right)=\left(x+y\right)\left(x^2+y^2-xy\right)\)

d)  \(\dfrac{x^2+y^2}{\left|x-y\right|}\)

\(=\dfrac{\left(x+y\right)^2-2xy}{\sqrt{x-y}^2}\)

\(=\dfrac{\left(x+y\right)^2-2xy}{\sqrt{x^2-2xy+y^2}}\)

\(=\dfrac{\left(x+y\right)^2-2xy}{\sqrt{x^2+y^2-2xy}}\)

`(-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