a) \(4x^2-1-x\left(2x+1\right)=0\)
\(\Leftrightarrow\left(2x-1\right)\left(2x+1\right)-x\left(2x+1\right)=0\)
\(\Leftrightarrow\left(2x+1\right)\left(2x-1-x\right)=0\)
\(\Leftrightarrow\left(2x+1\right)\left(x-1\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}2x+1=0\\x-1=0\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=-\frac{1}{2}\\x=1\end{cases}}\)
b) \(\left(4x-1\right)^2-9=0\)
\(\Leftrightarrow\left(4x-1-3\right)\left(4x-1+3\right)=0\)
\(\Leftrightarrow\left(4x-4\right)\left(4x+2\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}4x-4=0\\4x+2=0\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=1\\x=-\frac{1}{2}\end{cases}}\)
\(\)
a, x=-1/2 hoặc 1
b, x=-1/2 hoặc x=1
P/s sai thì sửa nha
