Document

Section 10.3 โ€“ The Integral Test
Positive Series:
A series whose elements are non-negative.
The Integral Test:
Let f be a continuous, positive and decreasing function and
๐’‚๐’ = ๐’‡(๐’™) for all positive integers, then
โˆž
โˆž
๐’=๐Ÿ ๐’‚๐’ converges iff the improper integral ๐Ÿ ๐’‡ ๐’™ ๐’…๐’™ converges
If the improper integral diverges, then the series diverges.
Section 10.3 โ€“ The Integral Test
Example:
๏‚ฅ
1
๏ƒฅ
n๏€ฝ1 n ๏€ซ 3
๏ƒฒ
1
b
lim ln| u|1
b๏‚ฎ ๏‚ฅ
๏‚ฅ
1
dx
x๏€ซ3
lim ๏ƒฒ
b๏‚ฎ ๏‚ฅ
lim ln| x ๏€ซ 3|1
b
b๏‚ฎ ๏‚ฅ
b
1
1
dx
x๏€ซ3
u ๏€ฝ x ๏€ซ 3 du ๏€ฝ dx
lim ๏›ln(b ๏€ซ 3) ๏€ญ ln(1 ๏€ซ 3)๏
b๏‚ฎ ๏‚ฅ
lim ๏ƒฒ
b๏‚ฎ ๏‚ฅ
๏‚ฅ ๏€ญ ln 4
b
1
1
du
u
๏œ divergent
Section 10.3 โ€“ The Integral Test
Positive Series
โˆž
p-Series
๐’=๐Ÿ
๐Ÿ
๐’๐’‘
p is a constant
If p is ๏€พ 1, then the series converges.
If p is ๏‚ฃ 1, then the series diverges.
โˆž
๐’=๐Ÿ
๐Ÿ
๐’๐’‘
โˆž
1
1
๐‘‘๐‘ฅ
๐‘
๐‘ฅ
๐‘
lim
๐‘โ†’โˆž
1
1
๐‘‘๐‘ฅ
๐‘
๐‘ฅ
๐‘ฅ โˆ’๐‘+1 ๐‘
lim
๐‘โ†’โˆž โˆ’๐‘ + 1 1
1
1
lim ๐‘โˆ’1 โˆ’ 1
1 โˆ’ ๐‘ ๐‘โ†’โˆž ๐‘
1
1 ๐‘
lim ๐‘โˆ’1
1 โˆ’ ๐‘ ๐‘โ†’โˆž ๐‘ฅ
1
Section 10.3 โ€“ The Integral Test
Positive Series
Examples:
โˆž
๐’=๐Ÿ
๐Ÿ
๐’๐Ÿ’
โˆž
๐’
๐’=๐Ÿ
๐Ÿ
โˆ’๐Ÿ
๐’‘ โˆ’ ๐’”๐’†๐’“๐’Š๐’†๐’”
โˆž
๐Ÿ
๐Ÿ
๐’=๐Ÿ ๐’ ๐Ÿ
๐’‘=๐Ÿ’>๐Ÿ
๐’‘ โˆ’ ๐’”๐’†๐’“๐’Š๐’†๐’”
converges
๐Ÿ
๐’‘ = โ‰ค ๐Ÿ diverges
๐Ÿ
Section 10.3 โ€“ The Integral Test
Harmonic Series
โˆž
๐’=๐Ÿ
๐Ÿ
๐’
Positive Series
๐’‘ โˆ’ ๐’”๐’†๐’“๐’Š๐’†๐’”
๐’‘=๐Ÿโ‰ค๐Ÿ
diverges
Section 10.3 โ€“ The Integral Test
Section 10.4 โ€“ Comparison Tests
Positive Series
Comparison Test (Ordinary Comparison Test)
โˆž
Let
๐‘ผ๐’ be a positive series.
๐’=๐Ÿ
โˆž
If
๐‘ฝ๐’ is a positive convergent series and ๐ŸŽ โ‰ค ๐‘ผ๐’ โ‰ค ๐‘ฝ๐’ ,then
๐’=๐Ÿ
the series
โˆž
If
โˆž
๐’=๐Ÿ ๐‘ผ๐’
converges.
๐‘ฝ๐’ is a positive divergent series and ๐ŸŽ โ‰ค ๐‘ฝ๐’ โ‰ค ๐‘ผ๐’ ,then
๐’=๐Ÿ
the series
โˆž
๐’=๐Ÿ ๐‘ผ๐’
diverges.
Section 10.4 โ€“ Comparison Tests
Positive Series
Examples:
โˆž
๐’=๐Ÿ
๐Ÿ’
๐Ÿ‘๐’ + ๐Ÿ
๐Ÿ’
๐‘ผ๐’ = ๐’
๐Ÿ‘ +๐Ÿ
๐Ÿ’
๐Ÿ’ ๐Ÿ’ ๐Ÿ ๐Ÿ’ ๐Ÿ
๐‘ฝ๐’ = ๐’ = + โˆ™ +
๐Ÿ‘
๐Ÿ‘ ๐Ÿ‘ ๐Ÿ‘ ๐Ÿ‘ ๐Ÿ‘
๐‘ˆ๐‘› โ‰ค ๐‘‰๐‘›
๐‘ฝ๐’ is a geometric series.
๐Ÿ’
๐Ÿ
๐’‚ = ,๐’“ = < ๐Ÿ
๐Ÿ‘
๐Ÿ‘
๐‘ฝ๐’ is a convergent geometric series.
โˆด ๐‘ผ๐’ is a convergent series.
๐Ÿ
+โ‹ฏ
Section 10.4 โ€“ Comparison Tests
Limit Comparison Test
Positive Series
โˆž
Let
๐‘ผ๐’
be a positive series and ๐‘ผ๐’ is a rational expression.
๐’=๐Ÿ
Choose ๐‘ฝ๐’ to be a positive series. If
๐‘ˆ๐‘›
lim
๐‘โ†’โˆž ๐‘‰๐‘›
= ๐ฟ, then
โˆž
๐’=๐Ÿ ๐‘ผ๐’
will converge or diverge depending on
โˆž
๐’=๐Ÿ ๐‘ผ๐’
will converge if
โˆž
๐’=๐Ÿ ๐‘ผ๐’
will diverge if
โˆž
๐’=๐Ÿ ๐‘ฝ๐’
โˆž
๐’=๐Ÿ ๐‘ฝ๐’
โˆž
๐’=๐Ÿ ๐‘ฝ๐’
provided ๐ŸŽ < ๐‘ณ < โˆž.
converges provided ๐‘ณ = ๐ŸŽ.
diverges provided ๐‘ณ = โˆž.
Section 10.4 โ€“ Comparison Tests
Positive Series
Examples:
โˆž
๐’=๐Ÿ
๐Ÿ
๐’๐Ÿ
๐‘ฝ๐’ =
๐Ÿ
+๐Ÿ
๐Ÿ‘
๐Ÿ
๐Ÿ
lim
๐‘›โ†’โˆž
๐’๐Ÿ
+๐Ÿ
๐Ÿ
๐’
๐Ÿ
2
๐Ÿ
๐Ÿ‘
lim
๐‘›โ†’โˆž
=
๐Ÿ
๐Ÿ
๐Ÿ‘
๐’
๐’
๐’๐Ÿ
๐Ÿ
๐’
๐Ÿ‘
+๐Ÿ
๐Ÿ
๐‘ฝ๐’ is a p-series.
๐Ÿ
๐Ÿ
๐Ÿ‘
lim
๐Ÿ‘
๐‘›โ†’โˆž
๐Ÿ
๐’‘= <๐Ÿ โˆด
๐Ÿ‘
๐’๐Ÿ
๐’๐Ÿ
1
+๐Ÿ
3
๐Ÿ
๐Ÿ‘
โˆž
๐’=๐Ÿ ๐‘ฝ๐’
is div.
๐‘›2
lim
๐‘›โ†’โˆž ๐‘›2 + 2
1
3
๐Ÿ‘
๐‘›
lim
๐‘›โ†’โˆž ๐‘›2 + 2
1
3
=1
๐‘ณ=๐Ÿ
0 < 1 < โˆž,
โˆž
๐’=๐Ÿ ๐‘ฝ๐’
is div.
โˆด โˆž
๐’=๐Ÿ ๐‘ผ๐’ is div.