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Understand limits involving infinity, vertical and horizontal asymptotes in calculus. Learn definitions, examples, and computational methods. Find horizontal and vertical asymptotes for given curves easily.
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Math 1304 Calculus I 2.6 – Limits involving Infinity, Asymptotes
Recall: Vertical Asymptotes • Definition: The line x = a is called a vertical asymptote of the curve y = f(x) if any of the following limits exist
Limits as x approaches ±infinity Now consider:
Basic Examples • f(x) = 1/x • f(x) = 1/(x-a) • f(x) = 1/x2 • f(x)= 1/(x-a)2
Def of Limit as x approaches infinity • Definition: Let f be a function defined on some interval (a,). We say that the limit as x approaches infinity is L if for any >0 there is a number N such that |f(x)-L|< whenever x > N. In this case we write
Def of Limit as x approaches -infinity • Definition: Let f be a function defined on some interval (-,a). We say that the limit as x approaches minus infinity is L if for any >0 there is a number N such that |f(x)-L|< whenever x < N. In this case we write
Def of Limit of infinity as x approaches infinity • Definition: Let f be a function defined on some interval (a,). We say that the limit as x approaches infinity is infinity if for any M there is a number N(M) such that f(x)>M whenever x > N(M). In this case we write
Horizontal Asymptotes • Definition: The line y = L is called a horizontal asymptote of the curve y = f(x) if either of the following limits exist
Computational Methodsfor limits as x approaches +-infinity • Rules • Basic functions: constants, 1/x, 1/xr • Sum, difference, product, quotient, power, etc. • Algebraic Techniques • For quotient of polynomials, divide by highest power (example next)
Examples • Find all horizontal and vertical asymptotes of the curve y=(2x-1)/(5x+3) • Find all horizontal and vertical asymptotes of the curve y=(2x2-1)/(3x2+3x+6)