Answer
$R_{1}=k\cdot \frac{L_{1}}{r_{1}^{4}}$
Work Step by Step
We are given:
$$R=k\cdot \dfrac{L}{r^{4}}\quad\quad(1)$$
We replace $R=R_1$, $r=r_1$, $R=R_1$ in equation $(1)$:
$R_{1}=k\cdot \dfrac{L_1}{r_{1}^{4}}$
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