ĐKXĐ: \(x\ge-\dfrac{1}{2}\)
\(4x^3+4x^2-5x+9=4\sqrt[4]{\left(2x+1\right).2.2.2}\le2x+1+2+2+2\)
\(\Leftrightarrow4x^3+4x^2-7x+2\le0\)
\(\Leftrightarrow\left(x+2\right)\left(2x-1\right)^2\le0\)
\(\Leftrightarrow\left(2x-1\right)^2\le0\) (do \(x+2>0\) ; \(\forall x\ge-\dfrac{1}{2}\))
\(\Rightarrow x=\dfrac{1}{2}\)
Vậy pt có nghiệm duy nhất \(x=\dfrac{1}{2}\)