Question

Tìm x , biết 4x² -9 + (2x -3).(x+7) = 0

Answer 1

\(4x^2-9+\left(2x-3\right)\left(x+7\right)=0\)

\(\Rightarrow\left(4x^2-9\right)+\left(2x-3\right)\left(x+7\right)=0\)

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

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

\(\Rightarrow\left(2x-3\right)\left(3x+10\right)=0\\ \Rightarrow\left[{}\begin{matrix}2x-3=0\\3x+10=0\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=\dfrac{3}{2}\\x=-\dfrac{10}{3}\end{matrix}\right.\)