Mathematics for Applied Sciences (Osnabrück 2011-2012)/Part I/Exercise sheet 4
- Warm-up-exercises
Exercise
Establish, for each , whether the function
is injective and/or surjective.
Exercise
Show that there exists a bijection between and .
Exercise
Give examples of mappings
such that is injective, but not surjective, and is surjective, but not injective.
Exercise
Let and be sets and let
be a function. Let
be another function such that and . Show that is the inverse of .
Exercise
Determine the composite functions and for the functions , defined by
Exercise
Let and be sets and let
and
be functions. Show that
Exercise *
Let be sets and let
be functions with their composition
Show that if is injective, then also is injective.
Exercise
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.
Exercise
Calculate in the polynomial ring the product
Exercise
Let be a field and let be the polynomial ring over . Prove the following properties concerning the degree of a polynomial:
Exercise
Show that in a polynomial ring over a field , the following statement holds: if are not zero, then also .
Exercise
Let be a field and let be the polynomial ring over . Let . Prove that the evaluating function
satisfies the following properties (here let ).
Exercise
Evaluate the polynomial
replacing the variable by the complex number .
Exercise
Perform, in the polynomial ring , the division with remainder , where , and .
Exercise
Let be a field and let be the polynomial ring over . Show that every polynomial , , can be decomposed as a product
where and is a polynomial with no roots (no zeroes). Moreover, the different numbers and the exponents are uniquely determined apart from the order.
Exercise
Let be a non-constant polynomial. Prove that can be decomposed as a product of linear factors.
Exercise
Determine the smallest real number for which the Bernoulli inequality with exponent holds.
Exercise
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 .
- ,
- ,
- ,
- ,
- ,
- ,
- .
Exercise
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
Exercise (3 marks)
Consider the set and the function
defined by the following table
Compute , that is the -rd composition (or iteration) of with itself.
Exercise (2 marks)
Prove that a strictly increasing function
is injective.
Exercise (3 marks)
Let be sets and let
be functions with their composite
Show that if is surjective, then also is surjective.
Exercise (3 marks)
Compute in the polynomial ring the product
Exercise (4 marks)
Perform, in the polynomial ring the division with remainder , where
and
Exercise (4 marks)
Let be a non-constant polynomial with real coefficients. Prove that can be written as a product of real polynomials of degrees or .