Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 2 - Limits - 2.8 Intermediate Value Theorem - Exercises - Page 86: 18

Answer

The IVT can be applied

Work Step by Step

The Intermediate Value Theorem "asks" for a function $f$ to be continuous on an interval $[a,b]$ so that $f(a)\not=f(b)$. Let's check these conditions for the given function. The interval $[a,b]$ is $[-1,1]$, so $a=-1,b=1$. $f(a)=f(-1)=-1$ $f(b)=f(1)=1^2=1$ Therefore $f(-1)\not=f(1)$. Now let's check the continuity. The function $f$ is continuous on each of the intervals $[-1,0)$ and $[0,1]$. We have to check the continuity at $x=0$. Calculate the left and right limits at $x=0$: $$\begin{align*} \lim_{x\rightarrow0^-}f(x)&=\lim_{x\rightarrow0^-} x=0\\ \lim_{x\rightarrow0^+}f(x)&=\lim_{x\rightarrow0^+} (x^2)=0^2=0\\ f(0)&=0 \end{align*}$$ As $\lim_{x\rightarrow0^-}f(x)=\lim_{x\rightarrow0^+}f(x)=f(0)$, it means the function is continuous at $x=0$. We conclude that the Intermediate Value Theorem can be applied.
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