Question

tìm x

a) (3x -1)^2 + (x + 3)^2 - 5 (2x - 3) ( x+ 3 ) = 0

b) x^2 - 4x + 4 -( x +3) ( x- 3) = 0

c) (5x + 1)^2 - (5x + 3)( 5x - 3) = 30

Answer 1

b) x^2 - 4x + 4 -( x +3) ( x- 3) = 0

\(\left(x^2-2.x.2+2^2\right)-\left(x^2-3^2\right)=0\)

\(\left(x-2\right)^2-\left(x^2-9\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}\left(x-2\right)^2=0\\\left(x^2-9\right)=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x-2=0\\x^2-9=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=2\\x^2=9\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=2\\x=3\end{matrix}\right.\)