Sem 1 Liebeck Flashcards
equality
exactly same elements
P=>Q
P implies Q
if P then Q
Q if P
P only if Q
negation p bar
If P=>Q
then Q bar => P bar
negation of for all
there exists
for all x statements in the empty set
always true
there exists an x statements in the empty set
always false
number systems rules
a+b = b+a
a+(b+c)=(a+b)+c
a(b+c)=ab+ac
between any 2 rationals…
there is another rational
if a is rational and b is irrational
a+b irrational
if a does not =0, ab irrational
if x does not = 1, then x + x^2 + x^3 +…+ x^n=
x(1-x^n) / 1-x
if -1<x<1, then x + x^2 + x^3 +… =
x / 1-x
if -1< x <1, then x + x^2 + x^3 +…=
1 / 1-x
every real number has decimal expression of form
x=a0.a1a2a3…
rational form of decimal steps
express as fractions over a power of 10
take out common factor to leave expression for geometric series
inequalities rules
- if x is a real number either x>0 or x<0 or x=0 and just one of these is true
- if x>y then -x<-y
- if x>y and c is a real number then x+c>y+c
- if x>0, y>0 then xy>0
- if x>y, y>z then x>z
how to find x in equations with modulus steps
- where does the modulus change?
- list cases for between each change
- case for both +ve, one +ve and one -ve and both -ve - evaluate inequality for each
- reach overall range based on cases
triangle inequality
|x+y| </= |x| + |y|
dividing complex numbers
multiply fraction by complex conjugate of denominator
how many complex roots does every quadratic have?
2
what is |z|
modulus of complex number
distance to origin
argument of complex number
angle between the positive x axis and line from z to the origin
polar form of a complex number
z=|z|(cosθ+isinθ)
adding multiples of 2pik does not change
principle argument
arg(z) between negative pi and positive pi
de moivre
z1z2=r1r2((cosθ1+θ2)+isin(θ1+θ2)
=r1r2e^i(θ1+θ2)
z^n=…
r^n(cosnθ+isinnθ)
z^-n
r^-n(cosnθ-isinnθ)
i theta form of complex numbers
z=re^iθ
e^iθ=e^i(θ+2kpi)
nth roots of unity
Zs that satisfy z^n=1
fundamental theorem of algebra
every polynomial equation of degree at least 1 has a root in C
polynomial of degree n factors into…
n linear equations
n roots in C
every real polynomial factorisies as a product of…
real linear and real quadratic polynomials
the non-real roots always…
come in complex conjugate pairs
(x-alpha)(x-beta)=
x^2-(alpha+beta)x + alphabeta
alpha+beta=-a
alphabeta=b
(x-alpha)(x-beta)(x-gamma)=
x^3+ax^2+bx+c
alpha+beta+gamma=-a
alphabeta+alphagamma+betagamma=b
alphabetagamma=c