Theo tc dãy tỉ số bằng nhau ta có 

\(x=\dfrac{y}{6}=\dfrac{z}{3}=\dfrac{2x-3y+4z}{2-18+12}=-\dfrac{24}{-4}=6\Rightarrow x=6;y=36;z=18\)

9x³y²

2xy x 3x²y + 3 = 6x³y² + 3

\(\left(-\dfrac{1}{3}\right)^2.\dfrac{4}{11}+\dfrac{7}{11}.\left(-\dfrac{1}{3}\right)^2\)

\(=\dfrac{1}{9}.\dfrac{4}{11}+\dfrac{7}{11}.\dfrac{1}{9}\)

\(=\dfrac{1}{9}.\left(\dfrac{4}{11}+\dfrac{7}{11}\right)\)

\(=\dfrac{1}{9}\)

Lời giải:
\((\frac{-1}{3})^2.\frac{4}{11}+\frac{7}{11}(\frac{-1}{3})^2=\frac{1}{9}.\frac{4}{11}+\frac{7}{11}.\frac{1}{9}\)

\(=\frac{1}{9}(\frac{4}{11}+\frac{7}{11})=\frac{1}{9}.\frac{11}{11}=\frac{1}{9}.1=\frac{1}{9}\)

Ai giải hộ mik đi ạ

\(m=\dfrac{2n-7}{n-5}\left(n\ne5\right)\).

Để m không là số âm -> (2n - 7) và (n - 5) cùng dấu.

TH1: (2n - 7) < 0 và (n - 5) < 0.

-> 2n < 7 và n < 5.

-> n < 3,5 và n < 5.

-> n < 3,5.

TH2: (2n - 7) > 0 và (n - 5) > 0.

-> 2n > 7 và n > 5.

-> n > 3,5 và n > 5.

-> n > 5.

Vậy n < 3,5 hoặc n > 5.

\(A=\dfrac{2\left(2n-1\right)+7}{2n-1}=2+\dfrac{7}{2n-1}\Rightarrow2n-1\inƯ\left(7\right)=\left\{\pm1;\pm7\right\}\)

mà A là số chình phương nên n = 1 

Ai trả lời mik đi ạ mik tick cho

\(\dfrac{4}{9}:(-\dfrac{1}{7})+6\dfrac{5}{9}.\dfrac{2}{3}\)

\(=\dfrac{4}{9}.(-7)+\dfrac{59}{9}.\dfrac{2}{3}\)

\(=\dfrac{-28}{9}+\dfrac{118}{27}\)

\(=\dfrac{34}{27}\)

\(=-\dfrac{28}{9}+\dfrac{59}{9}.\dfrac{2}{3}=\dfrac{-28}{9}+\dfrac{118}{27}=\dfrac{34}{27}\)

\(41-\left(2x-5\right)=3^2\\ 2x-5=41-9\\ 2x-5=32\\ 2x=37\\ x=\dfrac{37}{2}\)

`41 - ( 2.x - 5)  =3^2`

`41-(2.x-5)=9`

`2.x-5=41-9`

`2.x -5=32`

`2.x=32+5`

`2.x=37`

`x=37:2`

`x=37/2`

`x = 18,5`

`(-2)/7 xx x = 6/49`

`x  =6/49 : (-2)/7`

`x = 6/49 xx (-7)/2`

`x=(-3)/7`

____________________

`2/3x - 1/4 = -3 1/2`

`2/3x - 1/4 = (-7)/2`

`2/3x = (-7)/2 + 1/4`

`2/3x= (-13)/4`

`x = (-13)/4 : 2/3`

`x=(-13)/4 xx 3/2`

`x=(-39)/8`

__________________

`2/3 + 5/3 : x = 1/3`

`5/3 : x = 1/3 - 2/3`

`5/3 : x = (-1)/3`

`x = 5/3 : (-1)/3`

`x = 5/3 xx (-3)`

`x= (-15)/3`

`x=-5`

_______________________

`3/4 - ( x . (-1)/2) = 1 2/3`

`3/4 - ( x . (-1)/2) = 5/3`

`x . (-1)/2 = 3/4 - 5/3`

`x  .(-1)/2 = (-11)/12`

`x=(-11)/12 : (-1)/2`

`x=(-11)/12 xx (-2)`

`x=11/6`

_________________________

`#H.J`

a. \(-\dfrac{2}{7}\times x=\dfrac{6}{49}\\ x=\dfrac{6}{49}:-\dfrac{2}{7}\\ x=-\dfrac{3}{7}\)

b. \(\dfrac{2}{3}x-\dfrac{1}{4}=-3\dfrac{1}{2}\\ \dfrac{2}{3}x=-3\dfrac{1}{2}+\dfrac{1}{4}\\ \dfrac{2}{3}x=\dfrac{7}{6}+\dfrac{1}{4}\\ \dfrac{2}{3}x=\dfrac{17}{12}\\ x=\dfrac{17}{12}:\dfrac{2}{3}\\ x=\dfrac{17}{8}\)

c. \(\dfrac{2}{3}+\dfrac{5}{3}:x=\dfrac{1}{3}\\ \dfrac{5}{3}:x=\dfrac{1}{3}-\dfrac{2}{3}\\ \dfrac{5}{3}:x=-\dfrac{1}{3}\\ x=\dfrac{5}{3}:-\dfrac{1}{3}\\ x=-5\)

d. \(\dfrac{3}{4}-\left(x.-\dfrac{1}{2}\right)=1\dfrac{2}{3}\\ x.-\dfrac{1}{2}=\dfrac{3}{4}-\dfrac{5}{3}\\ x.-\dfrac{1}{2}=-\dfrac{11}{12}\\ x=-\dfrac{11}{12}:-\dfrac{1}{2}\\ x=\dfrac{11}{6}\)

\((-0,4)+2\dfrac{2}{5} . [(\dfrac{-2}{3})+1/2]^2\)

\(=(-0,4)+\dfrac{12}{5}. \dfrac{-1}{6}\)

\(=(-0,4)+(-0,4)=-0,8\)

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

\((\dfrac{7}{8}-0,25):(\dfrac{5}{6}-0,75)^2\)

\(=\dfrac{5}{8}:(\dfrac{1}{12})^2\)

\(=\dfrac{5}{8}:\dfrac{1}{144}\)

\(=90\)

cảm ơn

`(a-1)(x^2+1)-x(y+1)-(x+y^2-a-1)`

`=ax^2+a-x^2-1-xy-x-x-y^2+a+1`

`=ax^2-x^2-y^2-2x-xy+2a`