functions

Question 1

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

Answer 1

0 0 0 | c; c ≠ 0

Question 2

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

Answer 2

0 0 0 | 0

Question 3

distance between two points

Answer 3

= √((x2-x1)^2 + (y2-y1)^2)

Question 4

midpoint of a line segment

Answer 4

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

Question 5

when is a line completely vertical? horizontal?

Answer 5

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

Question 6

when are two lines parallel to each other? perpendicular?

Answer 6

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

Question 7

forms of a linear equation

Answer 7

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

Question 8

reciprocal functions

Answer 8

• zeros ⇒ poles (reciprocal value)
• poles ⇒ zeros (reciprocal value)
• minimum ⇒ maximum OR maximum ⇒ minimum (reciprocal value)
• horizontal asymptotes attain the reciprocal value

Question 9

qualities of compostion

Answer 9

• not commutative => the order of operations influences the result
• associative => change of grouping does not influence the result

Question 10

inverse function

Answer 10

• (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

Question 11

self-inverse functions

Answer 11

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

Question 12

when does a function f have an inverse function?

Answer 12

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

Question 13

transformations of functions

Answer 13

1. translation
2. reflection
3. shrinking/stretching

Question 14

translation

Answer 14

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

Question 15

reflection

Answer 15

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

Question 16

vertical stretching, shrinking

Answer 16

• 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 => stretching with 1/k

Question 17

horizontal stretching, shrinking

Answer 17

• vertical stretching: y = f(x/k)
• vertical shrinking: y = f(kx)
• stretching => dividing y with factor k
• shrinking => stretching with 1/k

Question 18

absolute value of a function

Answer 18

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

Question 19

squared functions

Answer 19

• 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

Question 20

even/odd functions

Answer 20

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

Question 21

vertex of a parabola

Answer 21

• V (h,k)
• h = (α1 + α2)/2 = -b/2a
• k = f(h) = -D/4a
• x = h => line of symmetry

Question 22

forms of a quadratic function

Answer 22

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)

Question 23

formula of a polynomial

Answer 23

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

Question 24

cubic, quadratic, linear term of a polynomial

Answer 24

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

Question 25

finding candidates for the roots of a polynomial

Answer 25

1. integer coefficients and integer root => ɑ divides the constant term in p
2. integer coefficients, rational root a/b => a divides the constant term in p, b divides the leading term

Question 26

remainder theorem

Answer 26

when dividing polynomial p(x) with linear polynomial (x - ɑ); ɑ∈R, the remainder is a constant p(ɑ)

Question 27

fundamental theorem of algebra

Answer 27

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

Question 28

factor theorem

Answer 28

p(x) has a factor (x - ɑ); ɑ∈R, iff p(ɑ) = 0

Question 29

graphs of polynomials

Answer 29

• smooth (no corners)
• no asymptotes
• one y-intercept
• n intercepts with the x-axis
• n-1 turning points

Question 30

behavior of the graph of a polynomial at the roots

Answer 30

• 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)

Question 31

drawing a polynomial

Answer 31

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

Question 32

Vieto’s formulae

Answer 32

sum of roots = - (an-1/an)
product of roots = a0/an