When we're dilating a line, we can either multiply the function value by a constant
[tex]f(x)\to kf(x)[/tex]or the argument of the function
[tex]f(x)\to f(kx)[/tex]Since the y-intercept of both functions is the same, then the multiplied quantity was the argument of the function.
We want to know the constant associated to the transformation
[tex]I(x)\to I(kx)=P(x)[/tex]We have the following values for both functions
[tex]\begin{gathered} I(-4)=4,\:I(4)=-2 \\ P(-2)=4,\:P(2)=-2 \end{gathered}[/tex]For the same y-value, we have the following correlations
[tex]\begin{gathered} I(-4)=P(-2)=P(\frac{1}{2}\cdot-4) \\ I(4)=P(2)=P(\frac{1}{2}\cdot4) \\ \implies I(x)=P(\frac{1}{2}x) \end{gathered}[/tex]and this is our answer.
[tex]I(x)=P(\frac{1}{2}x)[/tex]