Calculus: Early Transcendentals 8th Edition

Published by Cengage Learning
ISBN 10: 1285741552
ISBN 13: 978-1-28574-155-0

Chapter 3 - Section 3.1 - Derivatives of Polynomials and Exponential Functions - 3.1 Exercises - Page 182: 86

Answer

The equation of the tangent line is: $~~y = x-\frac{1}{4}$

Work Step by Step

$y = x^2$ $y = x^2-2x+2 = (x-1)^2+1$ A line that is tangent to both parabolas has a slope that is equal to the slope of each graph at the point where it meets the graph. We can see that the second parabola is simply the first parabola translated one unit to the right and one unit up. Therefore, a line that is tangent to both parabolas must have a slope of 1. We can find the point $x$ where the parabola $y = x^2$ has a slope of 1: $y = x^2$ $\frac{dy}{dx} = 2x = 1$ $x = \frac{1}{2}$ $y = (\frac{1}{2})^2 = \frac{1}{4}$ The slope of the tangent line is $1$ and the point $(\frac{1}{2},\frac{1}{4})$ is a point on the tangent line. We can find the equation of the line: $y - \frac{1}{4} = 1(x - \frac{1}{2})$ $y = x-\frac{1}{4}$
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