Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

Published by Pearson
ISBN 10: 0-32184-874-8
ISBN 13: 978-0-32184-874-1

Chapter 7 - Functions and Graphs - 7.5 Formulas, Applications, and Variation - 7.5 Exercise Set: 22

Answer

$r=\frac{nE-RI}{nI}$

Work Step by Step

Multiply $R+nr$ to both sides of the equation: $$\require{cancel} (R+nr) \cdot I=(R+nr)\cdot \frac{nE}{R+nr} \\(R+nr) \cdot I=\cancel{(R+nr)}\cdot \frac{nE}{\cancel{R+nr}} \\RI+nrI=nE$$ Subtract $RI$ to both sides: $$RI+nrI-RI=nE-RI \\nrI=nE-RI$$ Divide $(nI)$ to both sides: $$\frac{nrI}{nI}=\frac{nE-RI}{nI} \\r=\frac{nE-RI}{nI}$$
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