Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 3 - Section 3.6 - Rational Expressions - 3.6 Exercises - Page 309: 47

Answer

x-intercept: None y-intercept: (0, -9/8) Vertical Asymptote: x=4 Domain: (-∞, 4) U (4, ∞) Horizontal Asymptote: y=-1 Range: (-∞, -1) See graph below

Work Step by Step

$r(x)=\frac{-x^2 + 8x - 18}{x^2 - 8x + 16}$ $-x^2 + 8x - 18= 0$ $x^2 - 8x + 18 = 0$ $x^2 - 8x + 16 = -18 + 16$ No x-intercept y-intercept is the ratio of the constants, which is -18/16 = -9/8 Thus, the y-intercept is at (0, -9/8) Vertical asymptotes are when the denominator is equal to 0 $x^2 - 8x + 16 = 0$ $(x-4)^2 = 0$ x = 4 So, domain is from (-∞, 4) U (4, ∞) Horizontal asymptote is the ratio of the constants of the leading term (with equal degree) -1/1 = -1 Thus, the horizontal asymptote is at y=-1 So the range is from (-∞, -1)
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