Marginal effect with a dummy

Problem

Consider the model

\[y_i=β_1+β_2x_i+β_3x_i^2+γd_ix_i+ε_i\]

Find the marginal effect of \(x\) for individuals coded as \(d_i=1\) .

Solution

Answer: \(β_2+2β_3x_i+γ\)