Chapter 6 - Section 6.9 - Reciprocal Formulas Using a Calculator - Exercises - Page 261: 14

$R_{1}=238~\Omega$

Given $\frac{1}{R}=\frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}$ $R=145~\Omega, R_{1}=?, R_{2}=875~\Omega,R_{3}=645~\Omega$ $\frac{1}{145}=\frac{1}{R_{1}}+\frac{1}{875}+\frac{1}{645}$ $\frac{1}{R_{1}}=\frac{1}{145}-(\frac{1}{875}+\frac{1}{645})$ Therefore, $R_{1}=238~\Omega$ How to use the calculator: $145*x^{-1}-875*x^{-1}+645*x^{-1}=x^{-1}=$