bạn nào biết trả lời nhanh giúp mik nha

Mk nghĩ là :

a) 6

b) 24

a. \(x^2+y^2+z^2=xy+yz+xz\)

\(\Leftrightarrow x^2+y^2+z^2-xy-yz-xz=0\)

\(\Leftrightarrow2x^2+2y^2+2z^2-2xy-2yz-2zx=0\)

\(\Leftrightarrow\left(x-y\right)^2+\left(y-z\right)^2+\left(z-x\right)^2=0\)

Vì \(\hept{\begin{cases}\left(x-y\right)^2\ge0\\\left(y-z\right)^2\ge0\\\left(z-x\right)^2\ge0\end{cases}}\Leftrightarrow\hept{\begin{cases}x-y=0\\y-z=0\\z-x=0\end{cases}}\Leftrightarrow x=y=z\)( đpcm )

She has never known a more warmed-heart than her mother has.

=> Her mother has the most warm-hearted person She has ever known.

320 : ( x - 1 ) = ( 5³ - 5² ) : 4 + 15

<=> 320 : ( x - 1 ) = ( 125 - 25 ) : 4 + 15

<=> 320 : ( x - 1 ) = 100 : 4 + 15

<=> 320 : ( x - 1 ) = 40

<=> x - 1 = 8

<=> x = 9

240 : ( x - 5 ) = 2² . 5² - 20

<=> 240 : ( x - 5 ) = 4 . 25 - 20

<=> 240 : ( x - 5 ) = 80

<=> x - 5 = 3

<=> x = 8

70 : ( x - 3 ) = ( 3⁴ - 1 ) : 4 - 16

<=> 70 : ( x - 3 ) = 80 : 4 - 16

<=> 70 : ( x - 3 ) = 4

<=> x - 3 = 35/2

<=> x = 41/2

a) 320: (x-1) = (5³ - 5²):4 + 15         b) 240: (x-5) = 2².5² - 20      c) 70:(x-3) = (3⁴ - 1):4 - 16

    320: (x-1) = (125- 25): 4 + 15          240: (x-5) = 4.25 - 20            70:(x-3) = (81-1): 4 - 16

    320: (x-1) = 100:4 + 15                   240: (x-5) = 100 - 20              70: (x-3) = 80: 4 - 16

    320: (x-1) = 25 + 15                        240: (x-5) = 80                       70: (x-3) = 20  -16

    320: (x-1) = 40                                (x-5) = 240:80                        70: (x-3) = 4

    (x-1) = 320:40                                 (x-5) = 3                                 (x-3) = 70:4 

      (x-1) = 80                                      x = 5+3                                   (x-3) = 17,5

      x = 80+1                                        x = 8                                       x = 17,5 : 3

       x = 81                                                                                          x = 5,83 

We have never gone to Da Nang before

This is the first time we' ve gone to Da Nang

=> We have never gone to Da Nang

STUDY WELL ^^__^^

I began knowing her a long time ago

I have known her for a long time 

=> I began known her for a long time 

STUDY WELL ^^__^^

This is the first time his sister has bought a cheaper shirt than this one.

Hoặc là:

   This is the cheapest shirt his sister has bought.

1  cặp có giá trị là:

\(\frac{1}{11}\)+\(\frac{1}{25}\)=\(\frac{36}{275}\)

Có các phân số là;

(25-11):1+1=15(phân số)

Có các cặp là :

15 :2=7(CẶP ,DƯ 1 CẶP)

1 CẶP DƯ ĐÓ LÀ:

\(\frac{36}{275}\):2=\(\frac{36}{550}\)=\(\frac{18}{275}\)

Các cặp có tổng là:

\(\frac{36}{275}\).7=\(\frac{252}{275}\)

Tổng số đó là:

\(\frac{252}{275}\)+\(\frac{18}{275}\)=\(\frac{270}{275}\)=\(\frac{54}{55}\)

Phân số \(\frac{54}{55}\)lớn   hơn phân số \(\frac{47}{60}\)vì

\(\frac{54}{55}\)và \(\frac{47}{60}\)=\(\frac{3240}{3300}\)và \(\frac{2585}{3300}\)

\(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+\frac{1}{14}+...+\frac{1}{25}\)

\(=\left(\frac{1}{11}+\frac{1}{12}\right)+\left(\frac{1}{13}+\frac{1}{14}+\frac{1}{15}\right)+\left(\frac{1}{16}+\frac{1}{17}+\frac{1}{18}+\frac{1}{19}+\frac{1}{20}\right)+\left(\frac{1}{21}+\frac{1}{22}+\frac{1}{23}+\frac{1}{24}+\frac{1}{25}\right)\)

\(\frac{1}{11}+\frac{1}{12}>\frac{1}{12}+\frac{1}{12}=\frac{2}{12}=\frac{10}{60}\)

\(\frac{1}{13}+\frac{1}{14}+\frac{1}{15}>\frac{1}{15}+\frac{1}{15}+\frac{1}{15}=\frac{3}{15}=\frac{12}{60}\)

\(\frac{1}{16}+\frac{1}{17}+\frac{1}{18}+\frac{1}{19}+\frac{1}{20}>\frac{1}{20}+\frac{1}{20}+\frac{1}{20}+\frac{1}{20}+\frac{1}{20}=\frac{5}{20}=\frac{15}{60}\)

\(\frac{1}{21}+\frac{1}{22}+\frac{1}{23}+\frac{1}{24}+\frac{1}{25}>\frac{1}{25}+\frac{1}{25}+\frac{1}{25}+\frac{1}{25}+\frac{1}{25}=\frac{5}{25}=\frac{1}{5}=\frac{12}{60}\)

\(\Rightarrow\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+\frac{1}{14}+...+\frac{1}{25}>\frac{10}{60}+\frac{12}{60}+\frac{15}{60}+\frac{12}{60}=\frac{49}{60}\)

Mà \(\frac{49}{60}>\frac{47}{60}\)

\(\Rightarrow\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+\frac{1}{14}+...+\frac{1}{25}>\frac{47}{60}\left(đpcm\right)\)

I have never talk to such an intelligent girl.

ai giúp mình với

bấm máy tính cho nhanh haha :D