3. \(2x^2-9x+4=0\)

\[D=(-9)^2-4\cdot2\cdot4=81-32=49.\]

\[x_{1,2}=\frac{9\pm7}{4}.\]

\[x_1=4,\qquad x_2=\frac12.\]

Ответ: \(x=4\) и \(x=\frac12\).