sai đề :>>>

Trả lời :

Đề : 3x = 4y, y - x = 3

\(\Rightarrow\frac{x}{3}=\frac{y}{4}\)

Áp dụng tính chất dãy tỉ số bằng nhau ta có :

\(\Rightarrow\frac{x}{3}=\frac{y}{4}=\frac{y-x}{4-3}=\frac{3}{1}=3\)

\(\Rightarrow\hept{\begin{cases}\frac{x}{3}=3\\\frac{y}{4}=3\end{cases}\Rightarrow\hept{\begin{cases}x=9\\y=12\end{cases}}}\)

8+3.7=8+21=29

= 77 nhé

kb

hok tốt

\((x-3)(2x-7)=0\)

\(\Rightarrow\orbr{\begin{cases}x-3=0\\2x-7=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=3\\x=\frac{7}{2}\end{cases}}\)

Vậy \(x\in\left\{3;\frac{7}{2}\right\}\)

\(\left(x-3\right)\left(2x-7\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x-3=0\\2x-7=0\end{cases}\Rightarrow}\orbr{\begin{cases}x=3\\x=\frac{7}{2}\end{cases}}\)

Vậy ...

\(7^{2x}+7^{2x+3}=344\\ 7^{2x}\left(1+343\right)=344\\ 7^{2x}.344=344\\ 7^{2x}=1\\ 2x=0\\ x=0\)

Vậy x = 0

Ta có: \(7^{2x}+7^{2x+3}=344\)

\(\Leftrightarrow7^{2x}+7^{2x}\cdot7^3=344\)

\(\Leftrightarrow7^{2x}\left(1+7^3\right)=344\)

\(\Leftrightarrow7^{2x}=1\)

\(\Leftrightarrow2x=0\)

Vì 2>0

nên x=0

Vậy: x=0

=> x = 0 

vậy x = 0 :))

\(\dfrac{1}{6}+x=\dfrac{5}{12}\)
\(=>x=\dfrac{5}{12}-\dfrac{2}{12}=\dfrac{1}{4}\)
\(\dfrac{3}{4}+\dfrac{1}{4}x=-\dfrac{1}{2}\)
\(=>\dfrac{1}{4}x=-\dfrac{5}{4}\)
\(=>x=-\dfrac{5}{4}.4=-5\)
\(7^{2x}+7^{2x+3}=344\)
\(< =>49^x+49^x.343=344\)
\(=>x=?\)

Ta có : 2x + 12 = 3 . ( x - 7 )

           2x + 12 =  3x - 3 . 7 

           2x + 12 = 3x -21 

           2x + 12 + 21 = 3x 

           2x  + 33       = 3x 

                    33       =  3x - 2x 

                    x         = 33

\(2x+12=3\left(x-7\right)\)

\(\Leftrightarrow\)\(2x+12=3x-21\)

\(\Leftrightarrow\)\(3x-2x=12+21\)

\(\Leftrightarrow\)\(x=33\)

Vậy \(x=33\)

\(7^{2x}+7^{2x+3}=344\)

\(7^{2x}+7^{2x}.7^3=344\)

\(7^{2x}+7^{2x}.343=344\)

\(7^{2x}.1+7^{2x}.343=344\)

\(7^{2x}.\left(1+343\right)=344\)

\(7^{2x}.344=344\)

\(7^{2x}=344:344\)

\(7^{2x}=1\)

\(\Rightarrow7^{2x}=7^0\)

\(2x=0\)

\(x=0:2\)

\(x=0\)

\(7^{2x}+7^{2x+3}=344\\\Rightarrow7^{2x}+7^{2x}\cdot7^3=344\\\Rightarrow7^{2x}\cdot(1+7^3)=344\\\Rightarrow7^{2x}\cdot(1+343)=344\\\Rightarrow7^{2x}\cdot344=344\\\Rightarrow7^{2x}=1\\\Rightarrow2x=0\\\Rightarrow x=0\)