3rd Order Non Homogenous diff equation check!

Hi again all,

After solving my last problem i have a new one for you all, i`ve done it but not sure if it is correct!

$\displaystyle y1(x) = 1, y2(x) = cos 2x, y3(x) = sin 2x.$

Wronskian is 8

Find a (nonhomogeneous) third-order linear dierential equation with general so-

lution using the above

$\displaystyle y(x) = c1y1(x) + c2y2(x) + c3y3(x) + cos x:$

This is what i have,

$\displaystyle (m^2 + 4)(m-1)$

there for the equation is $\displaystyle m^3 - m^2 + 4m -4 =0$

hence Diff Equation is $\displaystyle y``` - y`` + 4y -4 = Cos(x)$

thanks

Funky