Solution:
Given:
[tex]\begin{gathered} P(x)=2x+1 \\ I(x)=P(\frac{1}{2}x) \end{gathered}[/tex]
[tex]\begin{gathered} I(x)=P(\frac{1}{2}x) \\ substituting\text{ }\frac{1}{2}x\text{ for }x\text{ into P\lparen x\rparen to get I\lparen x\rparen} \\ I(x)=2(\frac{1}{2}x)+1 \\ I(x)=x+1 \end{gathered}[/tex]
Therefore, I(x) = x + 1
