University Calculus: Early Transcendentals (3rd Edition)

Published by Pearson
ISBN 10: 0321999584
ISBN 13: 978-0-32199-958-0

Chapter 2 - Section 2.5 - Continuity - Exercises - Page 95: 58

Answer

All 5 statements ask for the same information, which is to find $x$ so that $x^3-3x-1=0$

Work Step by Step

(a) Find the roots of $f(x)=x^3-3x-1$ Roots of a function $f(x)$ are the values of $x$ such that $f(x)=0$. So basically, the statement asks to find $x$ so that $f(x)=0$. (b) Find the $x$-coordinates of the points where the curve $y=x^3$ crosses the line $y=3x+1$. To find the points of intersection, we set up an equation between 2 functions: $$x^3=3x+1$$ $$x^3-3x-1=0$$ So to find the $x$-coordinates of the points of intersections means to solve this equation, which is the same as to find $x$ so that $f(x)=x^3-3x-1=0$. (c) Find all the values of $x$ for which $x^3-3x=1$ $$x^3-3x=1$$ $$x^3-3x-1=0$$ Thus, the statement now also comes back to finding $x$ so that $f(x)=x^3-3x-1=0$. (d) Find the $x$-coordinates of the points where the cubic curve $y=x^3-3x$ crosses the line $y=1$ Again, like (b), finding points of intersection means setting up an equation between 2 functions: $$x^3-3x=1$$ $$x^3-3x-1=0$$ So again, to find the $x$-coordinates of the points of intersection goes back to finding all $x$ for which $f(x)=x^3-3x-1=0$ (e) Solve the equation $x^3-3x-1=0$ Solve the equation is a different way to say finding $x$ so that $f(x)=x^3-3x-1=0$ Therefore, overall, all 5 statements actually ask for the same information.
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