discrete_mathematics_with_a.../chapter_5/test_yourself.md
2026-06-28 16:44:40 -07:00

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**Test Yourself**
Page 296
1. The notation $\sum_{k = m}^{n}{a_k}$ is read "_____."
The summation from $k$ equals $m$ to $n$ of $a$ sub $k$.
2. The expanded form of $\sum_{k = m}^{n}{a_k}$ is _____.
$$ a_m + a_{m + 1} + a_{m + 2} + \dots + a_n $$
3. The value of $a_1 + a_2 + a_3 + \dots + a_n$ when $n = 2$ is "_____."
$$ a_1 + a_2 $$
4. The notation $\prod_{k = m}^{n}{a_k}$ is read "_____."
The product from $k$ equals $m$ to $n$ of $a$ sub $k$.
5. If $n$ is a positive integer, then $n! =$ _____.
$$ n \cdot (n - 1) \dots \cdot 3 \cdot 2 \cdot 1 $$
6. $\sum_{k = m}^{n}{a_k} + c\sum_{k = m}^{n}{b_k} =$ _____.
$$ \sum_{k = m}^{n}{a_k + cb_k} $$
7. $\left(\prod_{k = m}^{n}{a_k}\right)\left(\prod_{k = m}^{n}{b_k}\right) =$
_____.
$$ \prod_{k = m}^{n}{a_kb_k} $$
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**Test Yourself**
Page 309
1. Mathematical induction is a method for proving that a property defined for
integers $n$ is true for all values of $n$ that are _____.
greater than or equal to some initial value.
2. Let $P(n)$ be a property defined for integers $n$ and consider constructing a
proof by mathematical induction for the statement "P(n) is true for all
$n \geq a$."
a. In the basis step one must show _____.
that $P(a)$ is true.
b. In the inductive step one supposes that _____ for a particular but
arbitrarily chosen value of an integer $k \geq a$. This supposition is called
the _____. One then has to show that _____.
$P(k)$ is true; inductive hypothesis; $P(k + 1)$ is true.
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**Test Yourself**
Page 320
1. Mathematical induction differs from the kind of induction used in the natural
sciences because it is actually a form of _____ reasoning.
deductive
2. Mathematical induction can be used to _____ conjectures that have been made
using inductive reasoning.
prove
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**Test Yourself**
Page 333
1. In a proof by strong mathematical induction the basis step may require
checking a property $P(n)$ for more _____ value of $n$.
than one
2. Suppose that in the basis step for a proof by strong mathematical induction
the property $P(n)$ was checked for every integer $n$ from $a$ through $b$.
Then in the inductive step one assumes that for any integer $k \geq b$, the
property $P(n)$ is true for all values of $i$ from _____ through _____ and
one shows that _____ is true.
$a$; $k$; $P(k + 1)$
3. According to the well-ordering principle for the integers, if a set $S$ of
integers contains at least _____ and if there is some integer that is less
than or equal to every _____, then _____.
one integer; integer in $S$; $S$ contains a least element.
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**Test Yourself**
Page 346
1. A pre-condition for an algorithm is _____ and a post-condition for an
algorithm is _____.
2. A loop is defined as correct with respect to its pre- and post-conditions if,
and only if, whenever the algorithm variables satisfy the pre-condition for
the loop and the loop terminates after a finite number of steps, then _____.
3. For each iteration of a loop, if a loop invariant is true before iteration of
the loop, then _____.
4. Given a **while** loop with guard $G$ and a predicate $I(n)$ if the following
four properties are true, then the loop is correct with respect to its pre-
and post-conditions:
(a) The pre-condition for the loop implies that _____ before the first iteration
of the loop.
(b) For every integer $k \geq 0$, if the guard $G$ and the predicate $I(k)$ are
both true before an iteration of the loop, then _____.
\(c\) After a finite number of iterations of the loop, _____.
(d) If $N$ is the least number of iterations after which $G$ is false and $I(N)$
is true, then the values of the algorithm variables will be as specified _____.