Question

Answer 1

e: Ta có: \(3x^2-27\ge0\)

\(\Leftrightarrow3x^2\ge27\)

\(\Leftrightarrow x^2\ge9\)

\(\Leftrightarrow\left[{}\begin{matrix}x\ge3\\x\le-3\end{matrix}\right.\)

Answer 2

a: Ta có: 2x-1>0

\(\Leftrightarrow2x>1\)

hay \(x>\dfrac{1}{2}\)

b: Ta có: \(4-3x\le0\)

\(\Leftrightarrow3x\ge4\)

hay \(x\ge\dfrac{4}{3}\)

c: Ta có: \(2x^2-x-1>0\)

\(\Leftrightarrow2x^2-2x+x-1>0\)

\(\Leftrightarrow\left(x-1\right)\left(2x+1\right)>0\)

\(\Leftrightarrow\left[{}\begin{matrix}x>1\\x< -\dfrac{1}{2}\end{matrix}\right.\)