Using the Descarte’s rule of signs to determine the number of positive roots.

Using the Descarte’s rule of signs to determine the number of positive roots.

f(q)=[(k_f+k_d+k_p*(1-q))(\lambda_b* \gamma *q*P_Q+k_p*\lambda_r*(1-q)^2)+k_n*\lambda_b*\gamma*q*P_Q]*(\gamma*q*P_Q) - (I*\alpha)(\lambda_b* \gamma *q*P_Q+k_p*\lambda_r*(1-q)^2)(k_p*(1-q)*P_C)
.
Assume all the parameters are constant and could also combine parameters into single parameters for each term and call them something user friendly.

pls help me its really difficult form, i tried but didn't work