- Fibonacci sequences and numbers (7 exercices)
- Jointly defined sequences (final grades) (1 exercice)
- A little further: homographic sequences (3 exercices)
A0T0tt0
A1T1tt1
tt2
E.1874
Achilles
and
the
tortoise
(Zeno
of
Elea’s
paradox)
Problem
:
if
the
tortoise
is
ahead
of
Achilles,
Achilles
will
never
be
able
to
catch
up
with
it,
regardless
of
his
speed
;
for
when
Achilles
runs
to
reach
the
point
from
which
the
tortoise
started,
the
tortoise
moves
forward
in
such
a
way
that
Achilles
can
never
make
up
the
difference.
Let
us
assume
that
the
tortoise
has
a
one-meter
lead,
that
Achilles
runs
at
a
speed
of
2
m
=
s
and
the
tortoise
at
a
speed
of
1
m
=
s
.
Let
t
0
be
the
starting
time,
A
0
the
initial
position
of
Achilles,
and
T
0
that
of
the
tortoise.
t
1
is
the
moment
when
Achilles
reaches
the
turtle’s
previous
position.
Let
us
denote
this
position
by
A
1
.
The
turtle
con-tinues
to
move
forward
and
finds
itself
at
T
1
.
And
so
on.
Based
on
the
fact
that
Achilles’
and
the
tortoise’s
paths
can
be
divided
into
as
many
segments
as
(continuity
hypothesis)
,
it
is
believed
that
Achilles
will
never
catch
up
with
the
tor-toise,
as
there
will
always
be
a
portion
of
the
path
left
for
it
to
travel.
Another
problem
:
what
is
the
total
length
of
all
these
small
segments
when
placed
end
to
end?
In
other
words,
will
Achilles
catch
up
with
the
tortoise
infinitely?
1
Place
points
A
2
and
T
2
on
the
last
graduated
line
2
Give
the
values
of
T
0
−
A
0
,
T
1
−
A
1
,
T
2
−
A
2
.
3
We
accept
the
fact
that,
at
any
rank
in
the
study,
we
have
:
u
n
=
T
n
−
A
n
=
1
2
n
.
We
will
calculate
how
far
from
the
Achilles
point
the
par-ticipants
will
meet.
We
note
:
u
n
=
u
0
+
u
1
+
u
2
+
·
·
·
+
u
n
a
Expand
:
1
−
1
2
×
S
n
b
Deduce
:
S
n
=
1
−
1
2
n
+1
1
−
1
2
c
Give
the
limit
of
S
n
when
n
tends
towards
infinity,
which
we
note
as
:
lim
n
↦→
+
∞
u
0
+
u
1
+
·
·
·
+
u
n
ou
lim
n
↦→
+
∞
+
∞
k
=0
u
n
.
Note:
Zeno’s
paradoxes
were
reported
by
Aristotle
in
his
book
on
physics
(Book
VI)
.
We
could
also
have
considered
the
two
functions
that
as-
sociate
the
position
of
Achilles
and
the
tortoise
on
the
line
with
time
and
determined
the
point
of
intersection.
E.1875
The
discontinuity
(paradox
of
Zeno
of
Elia)
E.182
1
Consider
the
table
below
:
n
0
1
2
3
4
5
6
7
8
9
10
11
F
n
0
1
1
2
3
5
8
13
21
34
55
89
Show
that,
for
any
natural
integer
n
greater
than
2
,
the
numbers
F
n
verify
the
following
relationship
:
F
n
=
F
n
−
1
+
F
n
−
2
The
numbers
(
F
n
)
are
called
the
ˇ
numbers
of
Fibonacci
ı
;
any
sequence
of
numbers
exhibiting
such
a
relationship
will
be
said
to
be
of
ˇ
Fibonacci
suites
ı.
More
precisely,
the
sequence
studied
above
is
defined
by
the
initial
conditions
:
F
0
=0
;
F
1
=1
It
is
clear
that
:
lim
n
↦→
+
∞
F
n
=+
∞
.
We
will
now
study
the
ratio
of
two
consecutive
terms
;
i.e.
we
will
study
the
value
of
the
quotient
F
n
+1
F
n
when
n
becomes
larger
and
larger
(i.e.
when
n
tends
towards
+
∞
)
.
2
a
For
n
=2
,
establish
the
following
equality:
F
n
+1
F
n
=
2
b
Complete
the
following
table
to
within
10
−
5
:
n
1
2
3
4
5
6
7
8
9
10
F
n
+1
F
n
3
Make
a
conjecture
as
to
the
limit
of
the
sequence
(
F
n
)
and
the
golden
number
1+
5
2
.
We
will
now
show
that
all
Fibonacci
sequences
have
the
ratio
of
its
consecutive
terms
tending
towards
the
golden
number:
4
Noting
R
n
the
value
of
the
ratio
F
n
+1
F
n
,
show
that
:
R
n
=
1
+
1
R
n
−
1
5
Assuming,
that
the
sequence
(
R
n
)
admits
a
finite
limit
r
when
n
tends
to
+
∞
,
deduce
that
r
verifies
the
relation:
r
2
=
r
+
1
6
Verify
that
1+
5
2
and
1
−
5
2
are
two
numbers
verifying
this
equation.
7
Assuming
the
fact
that
a
second-degree
polynomial
can
only
cancel
in
at
most
two
values,
say
why
the
sequence
of
ratios
F
n
+1
F
n
necessarily
tends
to
1+
5
2
2.
Jointly
defined
sequences
(final
grades)
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E.5900
We
define
the
sequences
u
n
and
v
n
on
the
set
N
of
natural
numbers
by:
u
0
=
0
;
v
0
=
1
;
u
n
+1
=
u
n
+
v
n
2
v
n
+1
=
u
n
+
2
·
v
n
3
The
aim
of
this
exercise
is
to
study
the
convergence
of
the
sequences
u
n
and
v
n
.
Part
A
1
Calculate
u
1
and
v
1
.
2
Consider
the
function
f
extracted
from
an
algorithm
où
the
parameter
n
is
an
integer
greater
than
or
equal
to
1
:
Function
f(n)
u
←
0
v
←
1
For
k
varying
from
1
to
n
w
←
u
u
←
w+v
2
v
←
w+2
·
v
3
End
For
Return
(
u
;
v)
a
Call
the
function
f
with
the
value
n
=2
as
its
argument.
Copy
and
complete
the
table
below
showing
the
state
of
the
variables
during
the
call
to
the
function
f
.
k
w
u
v
1
2
b
For
a
given
integer
N
,
what
does
the
pair
of
values
returned
by
the
function
f
correspond
to
in
relation
to
the
situation
studied
in
this
exercise?
Part
B
1
a
Using
recursive
reasoning,
show
that,
for
any
natu-ral
number,
we
have
:
v
n
−
u
n
>
0
b
Deduce
that
the
sequence
u
n
is
an
increasing
se-quence
and
v
n
is
a
decreasing
sequence.
2
Justify
that
the
sequences
u
n
and
v
n
are
convergent.
Part
C
1
Consider
the
sequence
w
n
defined,
for
any
natural
num-ber
n
,
by:
w
n
=
v
n
−
u
n
a
Demonstrate
that
the
sequence
w
n
is
geometric.
b
Justify
that
the
limits
of
the
sequences
u
n
and
v
n
are
equal.
2
Consider
the
sequence
t
n
defined,
for
any
natural
num-ber
n
,
by:
t
n
=2
·
u
n
+3
·
v
n
a
Demonstrate
that
the
sequence
t
n
is
constant.
b
Deduce
the
expression
of
the
terms
of
the
sequence
u
n
as
a
function
of
n
.
c
Determine
the
limit
of
the
sequence
u
n
.
3.
A
little
further:
homographic
sequences
E.2454
Consider
the
sequence
u
n
n
∈
N
de-fined
by:
u
0
=
14
;
u
n
+1
=
10
·
u
n
−
1
u
n
+
8
for
any
n
∈
N
.
We
admit
that
the
sequence
u
n
is
defined
on
N
and
that
the
terms
of
the
sequence
are
strictly
greater
than
1
.
1
Shown
below
is
the
representative
curve
of
the
function
f
whose
image
of
x
is
defined
by
the
relation:
f
(
x
)
=
10
x
−
1
x
+
8
as
well
as
the
representation
of
the
first
bisector
of
the
plane
:
Show
the
first
five
terms
of
the
sequence
on
the
x-axis.
2
Consider
the
sequence
v
n
n
∈
N
defined
by
the
relation:
v
n
=
1
u
n
−
1
for
any
natural
number
n
.
a
Show
that
for
any
n
∈
N
,
we
have
:
v
n
+1
−
v
n
=
1
9
b
Give
the
explicit
formula
defining
each
term
of
the
se-quence
v
n
as
a
function
of
rank
n
.
c
Deduce
the
explicit
formula
defining
each
term
of
the
https://chingmath.fr
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sequence
u
n
as
a
function
of
rank
n
.
E.2414
Consider
the
sequence
u
n
n
∈
N
de-fined
:
u
0
=4
;
u
n
+1
=
−
u
n
+6
u
n
−
2
for
any
natural
number
n
.
1
Determine
the
first
three
terms
of
the
sequence
u
n
.
2
Let
v
n
n
∈
N
be
the
sequence
defined
by
the
relation:
v
n
=
u
n
+
2
u
n
−
3
for
any
natural
number
n
.
a
Determine
the
first
three
terms
of
this
sequence.
b
Show
that
:
v
n
+1
v
n
=
−
1
4
c
Deduce
the
nature
of
the
sequence
v
n
as
well
as
the
explicit
formula
determining
the
term
of
rank
n
as
a
function
of
n
.
3
a
Determine
the
expression
of
the
term
u
n
as
a
func-tion
of
the
term
v
n
.
b
Deduce
the
explicit
formula
defining
the
terms
of
u
n
as
a
function
of
n
.
E.5166
Consider
the
function
f
defined
on
−∞
;
8
by
the
relation:
f
(
x
)
=
4
·
x
+
4
−
x
+
8
In
the
orthonormal
reference
frame
O
;
I
;
J
below,
is
repre-sented
the
curve
C
f
representative
of
the
function
f
.
Consider
the
sequence
u
n
defined
by
the
relations
:
u
0
=
−
4
;
u
n
+1
=
f
u
n
for
all
n
∈
N
1
On
the
graph,
plot
the
first
five
terms
of
the
suite
u
n
on
the
x-axis.
2
By
calculation,
determine
the
exact
value
of
the
first
five
terms
of
the
sequence
u
n
.
3
Consider
the
sequence
v
n
defined
by
the
relation:
v
n
=
1
u
n
−
2
for
all
n
∈
N
a
Determine
the
first
five
terms
of
the
sequence
v
n
.
b
Make
a
conjecture
about
the
nature
of
the
sequence
v
n
and
the
value
of
its
characteristic
elements.
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