

8. Let f:D → R and let c be an accumulation point of D. Suppose that...
Please prove this, thanks!
2. Let {xn n21 be a sequence in R such that all n > 0. If ( lim supra) . (lim supー) = 1 Tn (here we already assume both factors are finite), prove that converges.
3. (a) (5 points) On the set A= R\{0}, let x ~ y if and only if x · y > 0. Is this relation an equivalence relation? Prove your answer. (b) (5 points) Let B = {1, 2, 3, 4, 5} and C = {1,3}. On the set of subsets of B, let D ~ E if and only if DAC = EnC. Is this relation an equivalence relation? Prove your answer.
Let U be an open subset of R". Let f: UCR" ->Rm. (a) Prove that f is continuously differentiable if and only if for each a e U, for eache > 0, there exists o > 0 such that for each xe U, if ||x - a| << ô, then |Df (x) Df(a)| < e.
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
5. Let A € Mnxn(C) with characteristic polynomial p(x) = cxºII-1(d; – x) and li + 0, Vi, a E Z>o. Show that if dim(ker(A))+k=n, then A= C2 for some complex matrix C.
Let z=5 where x, y, z E R. Prove that z? +z2+z?>
Find indicated quantity if it exists.
La x + 3 if x < -2 54. Let f(x) Find IVx+ 2 if x > -2 (A) lim+ f(x) (B) lim-f(x) (C) lim, f(x) (D) f(-2) x-27
5.3 Let F be an ordered field, let d > 0, and suppose that d does not have a square root in F. Let F(Vd) denote the set of all a+bvd, with a, b e F, where vd is a square root in some extension field of F (a) Show that F(Va) is a field. (b) Show how to define an ordering on FVa), with vd> 0, such that it becomes an ordered field
1 xe Let f(x)={? x 8. Prove that f(x) continuous only at +1. Let f(x)= $3.x xs! x >1 Using the definition prove lim f(x)=1 and lim f (x) = 3 x>17 11°
Let f : [a, b] → R and g : [a, b] → R be two continuous functions such that f(x) > g(x) for all x € (a,b]. 1. Show that there exists d > 0 such that f(x) > g(x) + 8 for all x € [a, b]. (Hint: introduce h := f -9] 2. Assume that g(x) > 0 for all x € [a, b]. Show that there exists k >1 such that f(x) > kg(x) for all...