Theorem 2.1: Let f: D-->R with x0 an accumulation point of D. Then f has a limit at x0 iff for each sequence {xn}^inf_n=1 convening to x0 with xn in D and xn≠x0 for all n, the sequence {f(x)} converges
Theorem 2.1: Let f: D-->R with x0 an accumulation point of D. Then f has a...
Let f : D → IR with x0 and accumulation point of D. f has a limit at x0 if and only if for each sequence {xn} ∞ n=1 converging to x0 with xn ∈ D and xn 6= x0 for all n, the sequence {f(xn)} ∞ n=1 converges. Let f:D + R with , and accumulation point of D. f has a limit at zo if and only if for each sequence {In}n=1 converging to to with In E...
+20 Problem 7. Let f :D + R, xo be an accumulation point of D and assume lim f(x) = L. Use the e-8 definition of the limit (not theorems or results from class or the text) to prove the following: (a) The function f is “bounded near xo”: there is an M ER and a 8 >0 such that for x E D, 0 < l< – xo<8 = \f(x) < M. Hint: compare with the proof that a...
Theorem 10.1.15 (Chain rule). Let X, Y be subsets of R, let xo e X be a limit point of X, and let yo e Y be a limit point of Y. Let f : X+Y be a function such that f(xo) = yo, and such that f is differentiable at Xo. Suppose that g:Y + R is a function which is differentiable at yo. Then the function gof:X + R is differentiable at xo, and .. (gºf)'(xo) = g'(yo)...
3-2. Prove Theorem 3.2. Theorem 3.2 Let I S R be an open interval, xe I, and let f. 8:1\{x} → R be functions. If there is a number 8 > 0 so that f and g are equal on the subset 12 € 7\(x): 13-X1 < 8 of I\(x), then f converges at x iff g converges at x and in this case the equality lim f(x) = lim g(z) holds.
1) Suppose f (a, b) R is continuous. The Carathéodory Theorem says that f(x) is differentiable at -cE (a, b) if 3 (a, b)-R which is continuous, and so that, (a) Show, for any constant a and continuous function (x), that af(x) is continuous at z-c by finding a Carathéodory function Paf(x). (b) Show, for any constants a, B, that if g : (a, b) -R is differentiable at c, with Carathéodory function pg(z), then the linear combination of functions,...
4. Suppose f : D → R is a function and a ∈ R, and that for some β > 0, D contains (a-β, a + β)-{a} = (a-β, a) U (a, a + β). Prove that limx→a f(x) = L if and only if for all ε > 0 there exists δ > 0 such that if 0 < lx-al < δ and x ∈ D, then If(x) - L| < εDefinition: Suppose f : D → R is a function, a...
1-> X- Let f :S → R and g:S → R be functions and c be a cluster point. Assume lim f (x), lim g(x) exists. Using the definition of the limit prove the following lim(af (x) + Bg(x)) =a lim f(x) + Blim g(x) for any a,ßeR xc XC X-> b. lim( f(x))} = (lim f(x)) f(x) lim f (x) c. If (Vxe S)g(x) # () and lim g(x)() then prove lim X-C XC 10 g(x) lim g(x) X-C
2. Let {xn}nEN be a sequence in R converging to x 0. Show that the sequence R. Assume that x 0 and for each n є N, xn converges to 1. 3. Let A C R". Say that x E Rn is a limit point of A if every open ball around x contains a point y x such that y E A. Let K c Rn be a set such that every infinite subset of K has a limit...
R i 11. Prove the statement by justifying the following steps. Theorem: Suppose f: D continuous on a compact set D. Then f is uniformly continuous on D. (a) Suppose that f is not uniformly continuous on D. Then there exists an for every n EN there exists xn and > 0 such that yn in D with la ,-ynl < 1/n and If(xn)-f(yn)12 E. (b) Apply 4.4.7, every bounded sequence has a convergent subsequence, to obtain a convergent subsequence...
8. Let f:D → R and let c be an accumulation point of D. Suppose that lim - cf(x) > 1. Prove that there exists a deleted neighborhood U of c such that f(x) > 1 for all 3 € Un D.