Question

tìm x, biết:

a) x( 5 + 3x ) - (x+ 1)(3x - 2 ) = 12         b) 13x(x-8) - x + 8 = 0

 

Answer 1

a) \(x\left(5+3x\right)-\left(x+1\right)\left(3x-2\right)=12\)

\(5x+3x^2-3x^2+2x-3x+2=12\)

\(4x=10\)

\(x=\frac{5}{2}\)

vậy \(x=\frac{5}{2}\)

\(13x\left(x-8\right)-x+8=0\)

\(13x\left(x-8\right)-\left(x-8\right)=0\)

\(\left(13x-1\right)\left(x-8\right)=0\)

\(\Rightarrow\orbr{\begin{cases}13x-1=0\\x-8=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{1}{13}\\x=8\end{cases}}\)

 vậy \(\orbr{\begin{cases}x=\frac{1}{13}\\x=8\end{cases}}\)