`81^8=3^x`

`=>3^x=(3^4)^8`

`=>3^x=3^32`

`=>x=32`

Vậy `x=32`

x=32

\(81^8=3^x\)

\(\Leftrightarrow\left(3^4\right)^8=3^x\)

\(\Leftrightarrow3^{32}=3^x\)

\(\Leftrightarrow x=32\)

PTHH:  2SO₂ + O₂ -> 2SO₃

Mary if she could speak some foreign languages
Lan if she was going to visit her aunt the day after
what I was doing
how she was feeling then
what I usually did in my free time
why he why he didn't come there to meet her
why I was so lazy and naughty
like playing soccer, don't you?
goes to school late, doesn't he?
can swim very well, can't you?
is going to the party, isn't she?
was published in Germany in 1550, wasn't it?
are sold all over the world, aren't they?
have been built this year, haven't they?
was given a book, wasn't he?
was bought by Mrs Brown yesterday, wasn't she?
is used every day, isn't it?
be beautiful sights in this village when I lived here

Bạn cảm ơn ai thế

cũng ko bt

Lời giải:

$\frac{x-2y}{3z}$ có thể nhận giá trị lớn nhất nếu $x$ lớn nhất và $y,z$ nhỏ nhất có thể.

$x$ lớn nhất có thể nhận là $14$ (theo điều kiện)

$y,z$ nhỏ nhất có thể nhận là $1,2$ (do $y,z$ phân biệt)

Nếu $x=14, y=1,z=2$ thì $\frac{x-2y}{3z}=2$

Nếu $x=14; y=2, z=1$ thì $\frac{x-2y}{3z}=\frac{10}{3}>2$

Đáp án D.

\(\Leftrightarrow4x^2=x+2+2\sqrt{x+2}+1\)

\(\Leftrightarrow\left(\sqrt{x+2}+1\right)^2=\left(2x\right)^2\)

\(\Rightarrow\left[{}\begin{matrix}\sqrt{x+2}+1=2x\\\sqrt{x+2}+1=-2x\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}\sqrt{x+2}=2x-1\left(x\ge\dfrac{1}{2}\right)\\\sqrt{x+2}=-2x-1\left(x\le-\dfrac{1}{2}\right)\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x+2=4x^2-4x+1\left(x\ge\dfrac{1}{2}\right)\\x+2=4x^2+4x+1\left(x\le-\dfrac{1}{2}\right)\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{5+\sqrt{41}}{8}\\x=-1\end{matrix}\right.\)