1. Sets

1.1 Relationships between Sets

disjoint: two sets have no elements in common at all

2. Real Number System

2.1 Surds

Surds are numbers constructed from applying a rational number power on a rational number. \[ Surds = \{p^q | p,q \in Q, p\geqslant0.\}\] The surds include all rational numbers but not vice versa

2.2 Transcendental numbers

The set of numbers which are not surd.

Surds + transcendental numbers = real numbers

3. Logarithm

3.1 Change of Base

\[ log_{m}a = \frac{log_{n}a}{log_{n}m} \quad for\quad n\ne 0\]

4. Functions

4.1 Characteristics

Injective: one-to-one \[ for \quad all \quad x_{1},x_{2} \in X, \quad then \quad f(x_{1}) = f(x_{2}) \Longleftrightarrow x_{1} = x_{2} \]

surjective: onto \[ for \quad y \in Y, there \quad exist \quad x \in X \quad such \quad that \quad f(x) = y \\ i.e. \quad Codomain = Range \]

bijective: if a function is both injective and surjective

4.2 Increasing and decreasing

Monotone increasing/decreasing: \[ for \quad all \quad x_{1},x_{2} \in X, \quad such \quad that \quad x_{1} < x_{2} \quad then \quad f(x_{1}) \le (\ge) f(x_{2})\]

Strictly increasing/decreasing: \[ for \quad all \quad x_{1},x_{2} \in X, \quad such \quad that \quad x_{1} < x_{2} \quad then \quad f(x_{1}) < (>) f(x_{2})\]

4.3 A catalog of essential functions

  • Polynomial

\[ P(x) = a_{n}x^n + a_{n-1}x^{n-1} + ... + a_{2}x^2 + a_{1}x + a_{0} \] * Power function

\[ f(x) = x^a, \quad where \quad a \quad is \quad a \quad constant \]

  • Rational function: a ratio of two polynomials

\[ f(x) = \frac{P(x)}{Q(x)} \]

  • Algebraic functions: a functionn is called an algebraic function if it can be constructed using algebraic operations (such as addition, division, and taking roots) starting with polynomials

  • Trigonometric functions: sine, cosine, tangant, cosecant, secant, and cotangent
  • Exponential functions:

\[ f(x) = b^x, where \quad b \quad is \quad a \quad positive \quad constant\]

  • Logarithmic functions

4.4 Transformations of functions

  • Vertical and horizontal shifts: Suppose c>0. To obtain the graph of
    • y = f(x-c), shift the graph of y=f(x) a distance c units to the right
    • y = f(x+c), shift the graph of y=f(x) a distance c units to the left
  • Vertical and horizontal stretching and reflecting: Suppose c>1. To obtain the graph of
    • y = f(cx), shrink the graph of y=f(x) horizontally by a factor of c
    • y = f(x/c), stretch the graph of y=f(x) horizontally by a factor of c

5. Polynomials

5.1 Remainder theorem:

Let f(x) be a real polynomial. The remainder of f(x) when divided by the expression (x-a) is given by f(a) \[ \frac{f(x)}{x-a} = g(x) + f(a) \] real polynomial: the coefficients are real numbers

5.2 Factor theorem:

Let f(x) be a real polynomial. The expression (x-a), where \(a \in R\) is a factor of f(x) if and only if f(a)=0