Foundations 1 Flashcards

(25 cards)

1
Q

Q: What is the base step in induction?

A

A: Verify the statement for the first integer (usually n=1).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Q: What makes strong induction “strong”?

A

A: You assume the statement is true for all numbers up to n, not just for n.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Q: Define factorial n!

A

A: n! = 1 · 2 · … · n with 0! = 1.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Q: What is (n choose k)?

A

A: n! / [k!(n−k)!].

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Q: State the binomial theorem.

A

A: (a+b)^n = Σ (n choose k) a^k b^{n−k}.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Q: Why is √2 irrational?

A

A: Assuming √2 = p/q leads to p and q both even, contradicting that the fraction is simplified.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Q: What is i²?

A

A: −1.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Q: Definition of modulus |z| of a+bi?

A

A: sqrt(a² + b²).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Q: Conjugate of a+bi?

A

A: a − bi.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Q: Polar form of a complex number?

A

A: z = r(cosθ + i sinθ).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Q: State De Moivre’s theorem.

A

A: (cosθ + i sinθ)^n = cos(nθ) + i sin(nθ).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Q: When is A ⇒ B false?

A

A: When A is true and B is false.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Q: Negation of “∀x, P(x)”

A

A: “∃x such that ¬P(x)”.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Q: What is a bijection?

A

A: A function that is both injective and surjective.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Q: How to test injectivity?

A

A: Show f(a)=f(b) ⇒ a=b.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Q: Three properties of an equivalence relation?

A

A: Reflexive, symmetric, transitive.

17
Q

Q: Group axioms?

A

A: Associativity, identity element, inverses, closure.

18
Q

Q: What is a homomorphism?

A

A: A map f satisfying f(xy)=f(x)f(y).

19
Q

Q: Define supremum.

A

A: Least upper bound of a set.

20
Q

Q: If a set has a maximum, what is the supremum?

A

A: The maximum itself.

21
Q

Q: Definition of convergence of a sequence?

A

A: a_n → L if for every ε>0, ∃N such that |a_n–L|<ε for n≥N.

22
Q

Q: What is a Cauchy sequence?

A

A: Terms get arbitrarily close to each other.

23
Q

Q: When does a geometric series converge?

A

A: When |r| < 1.

24
Q

Q: Ratio test result?

A

A: Converges if limit ratio < 1.

25
Q: What does it mean that ℝ is uncountable?
A: There is no bijection between ℕ and ℝ.