- Warm-up-exercises
Establish, for each
,
whether the function
-
is
injective
and/or
surjective.
Show that there exists a
bijection
between
and
.
Give examples of
mappings
-
such that
is
injective,
but not
surjective,
and
is surjective, but not injective.
Let
and
be sets and let
-
be a function. Let
-
be another function such that
and
.
Show that
is the
inverse
of
.
Determine the
composite functions
and
for the
functions
,
defined by
-
Let
and
be sets and let
-
-
and
-
be
functions.
Show that
-
![{\displaystyle {}H\circ (G\circ F)=(H\circ G)\circ F\,.}](https://wikimedia.org/api/rest_v1/media/math/render/svg/f4a511637a12636047c1ac0db916c90f2666c896)
Let
be sets and let
-
be
functions
with their
composition
-
Show that if
is
injective,
then also
is injective.
Let
-
be functions, which are increasing or decreasing, and let
be their
composition.
Let
be the number of the decreasing functions among the
's. Show that if
is even, then
is
increasing,
and if
is odd, then
is
decreasing.
Calculate in the
polynomial ring
the product
-
Let
be a field and let
be the polynomial ring over
. Prove the following properties concerning the
degree
of a polynomial:
-
![{\displaystyle {}\operatorname {deg} \,(P+Q)\leq \max\{\operatorname {deg} \,(P),\,\operatorname {deg} \,(Q)\}\,,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/b3a8ce0404f58829f08ff4d244c72c3fe796562a)
-
![{\displaystyle {}\operatorname {deg} \,(P\cdot Q)=\operatorname {deg} \,(P)+\operatorname {deg} \,(Q)\,.}](https://wikimedia.org/api/rest_v1/media/math/render/svg/6155f05f6c52942d5fba8639d141e60f03d1a88f)
Show that in a
polynomial ring
over a
field
, the following statement holds: if
are not zero, then also
.
Let
be a field and let
be the polynomial ring over
. Let
.
Prove that the evaluating function
-
satisfies the following properties
(here let
).
-
![{\displaystyle {}(P+Q)(a)=P(a)+Q(a)\,.}](https://wikimedia.org/api/rest_v1/media/math/render/svg/5fad78a123e99e89811832de92a9ce0420d63bc6)
-
![{\displaystyle {}(P\cdot Q)(a)=P(a)\cdot Q(a)\,.}](https://wikimedia.org/api/rest_v1/media/math/render/svg/da262e38a71464df7ce010f7450cd21972a9cdd2)
-
![{\displaystyle {}1(a)=1\,.}](https://wikimedia.org/api/rest_v1/media/math/render/svg/8906134ad3e345aa4335f32a84b45659f959435a)
Evaluate the
polynomial
-
replacing the variable
by the
complex number
.
Perform, in the polynomial ring
, the division with remainder
, where
,
and
.
Let
be a field and let
be the polynomial ring over
. Show that every polynomial
,
,
can be decomposed as a product
-
![{\displaystyle {}P=(X-\lambda _{1})^{\mu _{1}}\cdots (X-\lambda _{k})^{\mu _{k}}\cdot Q\,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/5fb27f1dab00668431a5b7bc0d34960909e92fa7)
where
and
is a polynomial with no roots (no zeroes). Moreover, the different numbers
and the exponents
are uniquely determined apart from the order.
Let
be a
non-constant
polynomial.
Prove that
can be decomposed as a product of
linear factors.
Determine the smallest real number for which the
Bernoulli inequality
with exponent
holds.
Sketch the graph of the following
rational functions
-
where each time
is the
complement set
of the set of the zeros of the denominator polynomial
.
,
,
,
,
,
,
.
Let
be a
polynomial
with
real
coefficients and let
be a
root
of
. Show that also the
complex conjugate
is a root of
.
- Hand-in-exercises
Consider the set
and the function
-
defined by the following table
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Compute
, that is the
-rd composition (or iteration) of
with itself.
Prove that a strictly increasing function
-
is injective.
Let
be sets and let
-
be
functions
with their
composite
-
Show that if
is
surjective,
then also
is surjective.
Compute in the
polynomial ring
the product
-
Perform, in the polynomial ring
the division with remainder
, where
-
![{\displaystyle {}P=(5+X^{2}+{\mathrm {i} }X+3-{\mathrm {i} })X^{4}+X^{2}+{\mathrm {i} }X+3-{\mathrm {i} }X^{2}+(3-2X^{2}+{\mathrm {i} }X+3-{\mathrm {i} })X-1\,}](https://wikimedia.org/api/rest_v1/media/math/render/svg/86955b125076af16afe619848e82fd1715f0e3c4)
and
-
![{\displaystyle {}T=X^{2}+{\mathrm {i} }X+3-{\mathrm {i} }\,.}](https://wikimedia.org/api/rest_v1/media/math/render/svg/ddfc63f197ba5f95144f666cccb5d48b0c1cadfd)
Let
be a non-constant polynomial with real coefficients. Prove that
can be written as a product of real polynomials of degrees
or
.