=>384-4x=352

=>4x=32

=>x=8

?
 

\(x^2-4x-320=0\)

\(\Leftrightarrow x^2-20x+16x-320=0\)

\(\Leftrightarrow x\cdot\left(x-20\right)+16\left(x-20\right)=0\)

\(\Leftrightarrow\left(x-20\right)\left(x+16\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-20=0\\x+16=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=20\\x=-16\end{matrix}\right.\)

\(\left\{{}\begin{matrix}4x+3y=320\\4x=5y\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}5y+3y=320\\4x=5y\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}8y=320\\4x=5y\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=40\\4x=5.40\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=40\\4x=200\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=40\\x=50\end{matrix}\right.\)

a) x = 320 - y
    y = 320 - x
b) 4x - y = 960
      4x   = 960 + y
        x = ( 960 + y ) : 4

x+y=320(*)

4x-y=960(**)

=> x+y+4x-y=320+960

=>5x=1280

=>x=256

Thay x=256 vào (*) suy ra y=64

Thử lại vào (**) thỏa mãn

Vậy x=256

       y=64

theo công thức ta có : 

(5+1)*(7+1)*(x+1)=352

6*8*(x+1)=352

x+1=22/3

x=19/3

tôi o chắc chắn

\(4^x+4^{x+1}=320\\ \Leftrightarrow4^x.\left(1+4\right)=320\\ \Leftrightarrow4^x.5=320\\ \Leftrightarrow4^x=\dfrac{320}{5}=64=4^3\\ Vậy:x=3\\ ----\\ 3^{x+3}-3^x=234\\ \Leftrightarrow3^x\left(3^3-1\right)=234\\ \Leftrightarrow3^x.26=234\\ \Leftrightarrow3^x=\dfrac{234}{26}=9=3^2\\ vậy:x=2\)

a: \(25496+28212:4\)

\(=25496+7053\)

=32549

b: \(\dfrac{\left(108610-87352\right)}{3}\)
\(=\dfrac{21258}{3}\)

\(=7086\)

a, -x+31=-69+39    

-x+31=-30

-x=-30-31

-x=-61

Vậy x=61

b -120+30+x=-50

-90+x=-50

x=-90--50

x=-40 

các câu còn lại cũng thế