Concept:
Work done by variable force:
\[
W = \int F \, dx
\]
Step 1:
\[
W = \int_{1}^{2} (2 + x)\, dx
\]
Step 2:
\[
W = \int_{1}^{2} 2 \, dx + \int_{1}^{2} x \, dx
\]
\[
= [2x]_1^2 + \left[\frac{x^2}{2}\right]_1^2
\]
Step 3:
\[
= (4 - 2) + \left(\frac{4}{2} - \frac{1}{2}\right)
= 2 + \frac{3}{2}
= \frac{7}{2}
\]
\[
W = 3.5 \, J
\]