Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 13 - Functions of Several Variables - 13.2 Exercises - Page 887: 8

Answer

The limit is $$\frac{\lim_{(x,y)\to(a,b)}(f(x,y)+g(x,y))}{\lim_{(x,y)\to(a,b)}f(x,y)}=\frac{7}{4}.$$

Work Step by Step

It is given that $$\lim_{(x,y)\to(a,b)}f(x,y)=4,\quad \lim_{(x,y)\to(a,b)}g(x,y)=3.$$ We will first use the rule that the limit of the quotient is the quotient of the limits: $$L=\lim_{(x,y)\to(a,b)}\frac{f(x,y)+g(x,y)}{f(x,y)}=\frac{\lim_{(x,y)\to(a,b)}(f(x,y)+g(x,y))}{\lim_{(x,y)\to(a,b)}f(x,y)}.$$ Now we will use the rule that the limit of the sum is the sum of the limits in the numerator: $$L=\frac{\lim_{(x,y)\to(a,b)}(f(x,y)+g(x,y))}{\lim_{(x,y)\to(a,b)}f(x,y)}=\\\frac{\lim_{(x,y)\to(a,b)}f(x,y)+\lim_{(x,y)\to(a,b)}g(x,y)}{\lim_{(x,y)\to(a,b)}f(x,y)} = \frac{4+3}{4}=\frac{7}{4}.$$
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