Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 10 - Section 10.1 - Systems of Linear Equations in Two Variables - 10.1 Exercises - Page 688: 5


$x=3$ $y=2$

Work Step by Step

$\begin{cases} x-y=1\\4x+3y=18\end{cases}$ Let $x-y=1$ be equation number 1 and $4x+3y=18$ be equation number 2: Solve for $x$ in equation 1: $x=1+y$ Let this equation be equation number 3 Substitute equation 3 in equation 2: $4x+3y=18$ $4(1+y)+3y=18$ $4+4y+3y=18$ Now, solve for $y$: $7y=18-4$ $7y=14$ $y=\dfrac{14}{7}=2$ Substitute $y=2$ in equation 3: $x=1+y$ $x=1+2=3$
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