functions Flashcards

1
Q

when does a system of linear equations not have a solution?

A

0 0 0 | c; c ≠ 0

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

when does a system of linear equations have infinite solutions, no unique solutions?

A

0 0 0 | 0

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

distance between two points

A

= √((x2-x1)^2 + (y2-y1)^2)

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

midpoint of a line segment

A

(x,y)
x = (x1+x2)/2
y = (y1+y2)/2

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

when is a line completely vertical? horizontal?

A

x1 = x2 ⇒ vertical line
y1 = y2 ⇒ horizontal line

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

when are two lines parallel to each other? perpendicular?

A

m1 = m2 ⇒ parallel lines
m1m2 = -1 ⇒ perpendicular lines

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

forms of a linear equation

A

general form: ax + by + c = 0
slope-intercept form: y = mx + b
slope-point form: y-y1 = m(x-x1)

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

reciprocal functions

A
  • zeros ⇒ poles
  • poles ⇒ zeros
  • minimum ⇒ maximum OR maximum ⇒ minimum (attains reciprocal value)
  • non-vertical asymptotes attain the reciprocal value
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

qualities of compostion

A
  • not commutative => the order of operations influences the result
  • associative => change of grouping does not influence the result
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

inverse function

A
  • (fof-1)(x) = x for all xDf and (f-1of)(x) = x for all xDf
  • drawn by reflecting across y=x
  • calculated by replacing the y and x
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

self-inverse functions

A

f(x) = f-1(x)
symmetrical across y=x

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

when does a function f have an inverse function?

A

if f is a one-to-one function (every two different originals have two different images, monotonic)
a function is not one-to-one => restrict the domain

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

transformations of functions

A
  1. translation
  2. reflection
  3. shrinking/stretching
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

translation

A

y = f(x) + k ⇒ up or down for k units
y = f(x + k) ⇒ left or right for k units
translation for vector (a,b) ⇒ y = f(x - a) + b

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

reflection

A

reflection through the x-axis ⇒ f(x) = -f1(x)
reflection through the y-axis ⇒ f(x) = f1(-x)

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

vertical stretching, shrinking

A
  • x-axis is fixed, in the y-direction
  • vertical stretching: y = kf(x)
  • vertical shrinking: y = f(x)/k
  • stretching => dividing y with factor k
  • shrinking => multiplying with k
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

horizontal stretching, shrinking

A
  • vertical stretching: y = f(x/k)
  • vertical shrinking: y = f(kx)
  • stretching => dividing x with factor k
  • shrinking => stretching with 1/k
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

absolute value of a function

A

y = |f(x)| ⇒ reflection of what is in the -y into +y
y = f(|x|) ⇒ reflection of what is in the +x on the -x

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

squared functions

A
  • f(x) → (f(x))2
  • values are non-negative
  • f(x) = 0, f(x) = 1 doesn’t change
  • 0 < f(x) < 1; f(x) > f(x)2
  • f(x) > 1; f(x) < f(x)2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

even/odd functions

A

Even ⇒ graph is symmetrical across the y-axis → f(-x) = f(x)
Odd ⇒ graph is symmetrical across the origin → f(-x) = -f(x)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

vertex of a parabola

A
  • V (h,k)
  • h = (α1 + α2)/2 = -b/2a
  • k = f(h) = -D/4a
  • x = h => line of symmetry
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

forms of a quadratic function

A

general form: f(x) = ax2 + bx + c
vertex form: f(x) = a(x - h)^2 + k
factorized form: f(x) = a(x - α1)(x - α2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

formula of a polynomial

A

p(x) = anxn + an-1xn-1 + … + a1x + a0
n is the degree of the polynomial (n∈N)
anxn = leading term (an = leading coefficient)
a0 = constant term

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

cubic, quadratic, linear term of a polynomial

A

a3x3 … cubic term
a2x2 … quadratic term
a1x … linear term

25
finding candidates for the roots of a polynomial
1. integer coefficients and integer root => **ɑ divides the constant coeff.** in p 1. integer coefficients, rational root a/b => **a divides the constant coeff.** in p, **b divides the leading coeff.**
26
remainder theorem
when dividing polynomial p(x) with linear polynomial (x - ɑ); ɑ∈R, the remainder is a constant p(ɑ)
27
fundamental theorem of algebra
every non-constant polynomial has a complex root => every non-constant polynomial of degree n1 can be factorised in n linear terms => a polynomial of degree n1 has n roots in C, some of which may be the same
28
factor theorem
p(x) has a factor (x - ɑ); ɑ∈R, iff p(ɑ) = 0
29
graphs of polynomials | smooth, asymptotes, intercepts w axes, turning points
* smooth (no corners) * no asymptotes * one y-intercept * n intercepts with the x-axis * n-1 turning points
30
behavior of the graph of a polynomial at the roots
* root of the first degree => crosses the x-axis as a straight line * even degree => lays down on the x-axis and bounces back (doesn't change in sign) * odd degree => lays down on the x-axis and crosses it (changes sign)
31
drawing a polynomial
1. calculate p(0) => first point 2. mark roots and their degrees 3. draw from the y-intercept into both directions p(0) = 0 => start drawing with the leading coefficient on the right side of the greatest root an > 0 => p(x)>0 an < 0 => p(x)<0
32
Vieto's formulae
sum of roots = - (an-1/an) product of roots = (a0/an)(-1)^n
33
rational function
f(x) = p(x)/q(x); where both p and q are polynomials
34
where are the zeros, poles, holes of a rational function?
* zeros = roots of the numerator * poles = roots of the denominator * hole = root of both the numerator and denominator, no longer a root of the denominator after cancelling out
35
where is the asymptote and what is the behaviour of the graph around it? | +when does it intersect the asymptote
* asymptote: y=k(x) (quotient of p/q) * graph always approaches, can intersect * intersection: where r(x) = 0
36
behaviour of the graph around **roots** based on multiplicity
* **degree 1** => sign changes, passes the x-axis as a straight line * **odd** => sign changes, appears as a straight line on the x-axis * **even** => sign remains, appears a straight line on the x-axis
37
behaviour of the graph around **poles** based on multiplicity
* **odd** multiplicity => sign **changes** * **even** multiplicity => sign **remains**
38
what is the non-vertical asymptote based on the degree of the num and den
* deg(num) > deg(den) => y≠0 * deg(num) < deg(den) => y=0 * deg(num) = deg(den) => y = ann/and
39
what is the exponential function?
f(x) = a^x; 0 < a < ∞, a≠1
40
key points of the exponential function
(0,1) and (1,a)
41
exponential growth
* a>1 * grows faster than any other polynomial * greater a, greater growth
42
exponential decay
* 0 < a < 1 * decays faster than any 1/polynomial * smaller a, greater decay
43
exponential model
**A(t) = Ao b^t** b > 1 => exponential growth 0 < b < 1 => exponential decay
44
half-life definition
= time it takes for a certain material to decrease to half its amount
45
formula for half-life
A(t) = Ao (1/2)^(t/h) h...half-life
46
natural constant
e = 2.71828 e = lim(x->∞) (1 + 1/n)^n e = 1 + 1/1! + 1/2! + 1/3! + ... + 1/n!
47
simple interest
P = P.(1+nr) n...time r...interest rate
48
compound interest
P = P. (1 + r/m)^nm r ... interest rate m ... number of componding nm ... compounding period
49
continuous compounding
P = P.e^(rn) n ... time
50
logarithm def
loga(b) = c <=> a^c = b a > 0, a ≠ 1, b > 0
51
inverse function of f(x) = a^x
f(x) = loga(x)
52
corollaries of the inverse function of f(x) = a^x being f(x) = loga(x)
loga(a^x) = x a^(loga(x)) = x
53
key points of the logarithmic function
(1, 0), (a, 1)
54
asymptote of the logarithmic function
x=0
55
increasing vs decreasing logarithmic function
0 decreasing (decreases slowly) a>1 => increasing (increases slowly)
56
change of base formula - exponents
a^x = b^((logb(a))(x))
57
properties of logarithms
loga(xy) = loga(x) + loga(y) loga(x/y) = loga(x) - loga(y) loga(x^k) = kloga(x) loga(x) = 1/logx(a)
58
change of base formula (logarithms)
loga(x) = logb(x)/logb(a)
59
when does the sign change in exponential/logarithmic functions
decreasing function is applied