/ , / .
: , / / .
.
() .
:
a b. e>0 a b s s': s ≤ a ≤ s', s ≤ b ≤ s', s' s e, a b (a = b).
:
, a < b. a < r < r1 < b, s < r < r1 < s' => s s' > r1 r > 0, s' s , .
:
α,β. α + β = γ , a + b < γ < a' + b', , a < α < a', b < β < b', a' a = e, b' b = e.
a < α < a', b < β < b', γ=αβ, ab < γ < a'b'.
1. γ = sup{ab}, ab < a'b'. α < a0', β < b0', a'<a0', b' < b0',
2. a'b' ab = a'(b'b) + b(a'a) <= (a0'+b0')((b'b) + (a'a)).
.
xn, ℰ > 0 N, n > N |xn a| < ℰ.
xn, ℰ > 0 () xn (aℰ, a+ℰ) n > N.
a ℰ < xn < a + ℰ
a = lim xn xn → a
, .
(c,d), , .
xn, .
N.
, xn → ∞, n → ∞, > 0 ∃ N: xn > E ∀ n > N.
(M, ∞) .
a, b, a < b, . . = lim xn, b = lim xn. ℰ = (ba)/4. (aℰ, a+ℰ), (bℰ, b+ℰ) ; a+ℰ > bℰ ; a+ℰ < bℰ .
|
|
∀ ℰ > 0 ∃ N: |xn a| < ℰ ∀ n > N
|xn| > |a|/2.
ℰ = |a|/2 ≠ 0 |a| |xn| ≤ |xn a| < |a|/2
( )
xn→ a, yn→ b ∀ n xn ≤ yn, a ≤ b.
:
lim xn/yn = lim xn / lim yn, lim yn ≠ 0
lim xn = a, lim yn = b: b ≠ 0
xn/yn a/b = (xn a)/yn a(yn b)/ynb
∃ N1: |yn| > |b|/2 (∀ n > N1)
|xn/yn a/b| < (2|xna|) / |b| + |ynb| (2|a|) / b2 (∀ n > N2)
∀ ℰ>0 ∃ N2: |xna|<ℰ (∀ n > N2)
N = max(N1,N2,N3)
|xn/yn a/b| < ℰ1 (∀ n > N) => ℰ1 = 2ℰ/|b| + (2ℰ|a|)/b2
|xn/yn a/b| < 2ℰ/|b| + (2ℰ|a|)/b2 (∀ n > N), , .
:
xn , n→∞lim xn = 0, . .
∀ ℰ>0 ∃ N: |xn|<ℰ ∀ n > N.
yn , n→∞lim yn = ∞, . .
∀ E>0 ∃ N: |yn|>E ∀ n > N.
(1) |xn| ≤ M ∀ n, yn → ∞ => lim xn/yn = 0
(2) |xn| ≥ m>0 ∀ n, yn → 0, yn ≠ 0 => lim xn/yn = ∞
(3) xn, yn xn+ yn.
(4) xn yn xnyn.
x1,x2,...,xn (), xn+1 ≥ xn.
x1,x2,...,xn (), xn+1 ≤ xn.
( ):
( ) . , . xn → +∞.
( ) . , . xn → ∞.
a = sup{xn}:
1) a ≥ xn ∀ n
2) ∀ ℰ>0 ∃ N: xn>aℰ
.
rn → α, α>0
rn = α0,α1α2...αn
e
yn+m yn = 1/(n+1)! + 1/(n+2)! + + 1/(n+m)! = 1/(n+m)! ⋅ (1 + 1/(n+2) + 1/(n+2)(n+3) + + 1/(n+2)..(n+m)) < 1/(n+1)! ⋅ (n+2)/(n+1)
(n+2)/(n+1)2 < 1/n
limm yn+m = e => 0 < e ym < 1/(n!⋅n)
z = (e yn)(n!⋅n)
0 < z < 1
z < zn
e = ym + z/(n!⋅n)
n = 5: z/(n!⋅n) < 1/(1⋅2⋅3⋅4⋅5⋅5) = 1/600
0 < e y5 < 1/600;
n = 5: z/(n!⋅n) < 1/(1⋅2⋅3⋅4⋅5⋅6⋅6) = 1/4320
0 < e y6 < 1/4320.
:
|
|
, x1,x2,...,xn , , ℰ > 0 e N, |xn xm| < ℰ n,m > N.
∀ ℰ > 0 ∃ N: |xn xm| < ℰ ∀ n,m > N
1) xn → a
|xn a| < ℰ/2 n>N
|xn xm| = |xn a (xm a)| <= |xn a| + |xm a| < ℰ/2 + ℰ/2 = ℰ n,m>N
.
A = {α ϵ R | ∃ N: xn > α ∀ n>N}
A' = {α' ϵ R | ∃ N: xn < α' ∀ n>N}
A U A' = O
α A, beta < α => beta A
xm ℰ < xn < xm + ℰ
xm ℰ ϵ A
xm + ℰ ϵ A'
α < α'
a = sup {α} = sup A
α ≤ a ≤ α
xm ℰ ≤ a ≤ xm + ℰ
|xm a| ≤ ℰ ∀ m>N ==> lim xm = a
:
an = a1,a2,a3,...,an
bn = b1,b2,b3,...,bn
an < bn ∀ n
an+1 ≥ an ∀ n
bn+1 ≤ bn ∀ n ==> bn an → 0 (n → ∞)
an ≤ bn ≤ b1 ==> lim an = c
bn ≥ an ≥ a1 ==> lim bn = c'
0 = lim(bn an) = lim bn lim an = c' c ==> c' = c
, , . an bn , , .